# Why Diesel Engines Lose Power & Efficiency Over Time



## alacey (Mar 14, 2018)

Interesting video from Jason Fenske at Engineering Explained on Exxon's new Synergy diesel fuel additive package, and their 2% mpg improvement claim. What I found more interesting was the 11% NOx improvement which means less DEF usage and/or more power could be had without the need to de-fuel in order to stay within emissions.

BTW, even though he doesn't name of the third party test facility, it was Southwest Research in south Texas. I recognize the facility from when I worked at Cummins(we used them a lot) and confirmed it with a few friends that work there.

Enjoy!

[url]https://youtu.be/xFJ3EHwM4ZQ[/URL]


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## Bolosman (Apr 5, 2017)

Slight deviation from the OP...

Had the inlet valves on mine walnut blasted around 3 weeks ago and its made a big difference when coasting i.e. car does not slow down as quickly as it used to which means i can come off the accelerator sooner. Couple this with a sharper throttle response and my MPG has increased by around 4-5 which is a rough estimate based on my regular commute to work. Cost was £350 here in the UK and the main driver for getting it done was to clean the whole inlet system of the car after deleting the EGR valve.


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## jfxogara (Oct 26, 2012)

Excellent video thanks for sharing.


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## alacey (Mar 14, 2018)

Yeah it is kind of interesting that they take fuel made by existing standards, add an additional additive to it, and shown an improvement. Who'd a thunk it.


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## Pierre Louis (Oct 23, 2011)

Am on my 7th diesel with most reaching way past 100,000 miles, hasn't happened to me yet. All keep their excellent fuel economy or, gasp, get better. Your mileage may vary....


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## alacey (Mar 14, 2018)

Pierre Louis said:


> Am on my 7th diesel with most reaching way past 100,000 miles, hasn't happened to me yet. All keep their excellent fuel economy or, gasp, get better. Your mileage may vary....


So how did you know none of those diesels never had buildup on the injectors? Did you tear the engine down or pull the injectors? How did you test that it got the same mileage through out their life? Did you regularly dyno the engine under the same cycles and got the same exact mileage or, gasp, even better? If so, may I see those records and the methods used? Also, what was your standard deviation of your test methods?

Just curious is all......


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## Autoputzer (Mar 16, 2014)

Marine diesel fuel is raunchy stuff with little or no additives. It's not regulated. Much of the pollution in port cities comes from ships. I used to work on ships that would spend hours creeping around at just a few knots. Every few hours they'd stop what they were doing, go out to deep water and do a "carbon burn run" at high speeds to clean out the injectors and combustion chambers.


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## SPL15 (Feb 3, 2019)

I always cringe at this guy's videos... Majority of the time he's fairly accurate & correct; however, I catch too much incorrect info, and / or overly simplified info to view him as credible, & nothing more than a paid shill / youtube hobbyist... Case in point @ 3:20 in the video, "They also tend to use turbo chargers, and as a result tend to have more torque..."... Umm, Nope, You Fail, again...

After an issue filling at a dilapidated BP fuel station (should have known better from just looking at the useless person working there), I use mobil synergy diesel exclusively these days regardless of prices elsewhere. Not because I've noticed a tangible difference, but because the station is pretty much brand new, super shiny & bright, as well as super busy where they're likely not going to have algae infested old diesel in their tanks. They're spending an awful lot on the markeneering behind this new diesel additive package, so I'd think / imagine (maybe more "imagine" than "think") they'd be more keen on ensuring that stations that serve it are maintained per some sort of standard to ensure their fancy fuel isn't contaminated w/ crap that'll certainly cause people not to visit their local higher priced Mobil fuel station...

Luckily no damage from the BP fuel up, but when draining the tank & removing the fuel filter, the diesel stunk like an old water tank full of algae & mildew... I only filled up around 3 gallons because it took forever & the fuel was foamy beyond belief... Drove straight home 2 miles & drained out over half a tank of fuel the next day...


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## Pierre Louis (Oct 23, 2011)

alacey said:


> So how did you know none of those diesels never had buildup on the injectors? Did you tear the engine down or pull the injectors? How did you test that it got the same mileage through out their life? Did you regularly dyno the engine under the same cycles and got the same exact mileage or, gasp, even better? If so, may I see those records and the methods used? Also, what was your standard deviation of your test methods?
> 
> Just curious is all......


I'll have to ask my mechanic how the cars did after he bought them from me. One car, a 2005 E320 CDI got better fuel economy by 200,000 miles and is running strong after 350,000 miles. I routinely did an "Italian tune-up" with it so I don't know if that helps.

Driving long distance in hot weather using busy-station brand-name diesel (mostly Shell and Chevron) and no aftermarket snake oil seems to do the trick for me.

I didn't say anything about power, but didn't notice much change. I obviously didn't compulsively calculate any standard deviation and do not purport any data, just testimonial.

I don't think there is much reason to worry about clogging up injectors if one uses properly additized retail diesel from a well-cared for station. Branded diesel, IMO, has a better chance of getting quality control by the company which has been my experience so far.


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## Autoputzer (Mar 16, 2014)

SPL15 said:


> I always cringe at this guy's videos... Majority of the time he's fairly accurate & correct; however, I catch too much incorrect info, and / or overly simplified info to view him as credible, & nothing more than a paid shill / youtube hobbyist... Case in point @ 3:20 in the video, "They also tend to use turbo chargers, *and as a result tend to have more torque.*.."... Umm, Nope, You Fail, again...


That passes my sniff check.

Turbocharging introduces more air into the combustion chamber. More air means more fuel can be introduced. More fuel means higher combustion temperature and pressure. More combustion chamber pressure means more force on the top of the pistons. More force on the top of the pistons means more torque.


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## alacey (Mar 14, 2018)

Pierre Louis said:


> I'll have to ask my mechanic how the cars did after he bought them from me. One car, a 2005 E320 CDI got better fuel economy by 200,000 miles and is running strong after 350,000 miles. I routinely did an "Italian tune-up" with it so I don't know if that helps.
> 
> Driving long distance in hot weather using busy-station brand-name diesel (mostly Shell and Chevron) and no aftermarket snake oil seems to do the trick for me.
> 
> ...


Well if it just as testimonial and you didn't do any scientific test with a very low margin for error, then how can you say that the scientific test used in the video with very low margin for error is wrong? It seems you are ignoring all data in order believe what you want to believe instead of looking at the facts and making an educated decision. In other words, you are letting your beliefs change the facts, and not the facts change your beliefs.

Also, the diesel fuel they were comparing it to was their own branded additized retail ASTM D975 diesel found in other branded fuel stations. They just added an additional additive(similar to how one may add an injector cleaner additive on their own vehicle) to help clean the injectors.

Lastly, this has more of an effect on modern diesels that use much higher pressures and smaller injector holes. The latest iteration of the CP4 is up to 2,700 bar, up from 1,800 bar in my 328d and 6.7L Cummins. Add that kind of pressure to smaller injector holes, and even the smallest of carbon build up could have a considerable effect on the injector spray pattern. Heck even the injector holes in my old 99 Cummins were noticeably larger than the ones on my 2014 Cummins. And yes, it did have buildup on the injector when i replaced them with performance 50 over injectors, and yes I only use branded fuel with no additives used in over three years on that engine.


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## alacey (Mar 14, 2018)

Autoputzer said:


> That passes my sniff check.
> 
> Turbocharging introduces more air into the combustion chamber. More air means more fuel can be introduced. More fuel means higher combustion temperature and pressure. More combustion chamber pressure means more force on the top of the pistons. More force on the top of the pistons means more torque.


I agree, although with a diesel the amount of air introduced is mainly regulated by the amount of fuel being added. With a gasser, it is as you stated since they have to stay around a 14.7:1 air duel ratio.

There are multiple reasons why diesels have more torque, with turbochargers being one of them, and he has covered these reasons in other videos.


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## Nyc Dito (Jun 11, 2015)

When its available i'll give it a shot. Last time I used Mobil diesel, my car didn't "feel" the same". 100% Placebo lol


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## FaRKle! (Jun 18, 2016)

So there's really only benefit if your injectors are already fouled. If you already use additives that should prevent fouling or a new-ish engine then you won't really see any improvement.

Makes sense then why I didn't see any difference when I tried it.


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## ard (Jul 1, 2009)

2%?!?!?!?!

Sign me up, more than happy to spend 10% more on synergy plus.

Quite the advertisement....


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## alacey (Mar 14, 2018)

ard said:


> 2%?!?!?!?!
> 
> Sign me up, more than happy to spend 10% more on synergy plus.
> 
> Quite the advertisement....


I am not sure what fuel prices in your area are, but Exxon Synergy stations here cost the same as any other branded diesel like Chevron and Shell station within a few miles from them.

The Exxon/Circle K in this Gasbuddy list is generally where I fill up on the way to work and it generally costs the same as the Walmart (Murphy) and Shell stations if not better.

Gasbuddy - 78130

Also, if you look at Engineering Explained YouTube library, you will see that Jason has done videos in collaboration with various oil/fuel companies and vehicle manufacturer so to say he adversities for one is a bit false.


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## FaRKle! (Jun 18, 2016)

Around me the stations I fill up at are $3.79-$3.85/gal (76, Valero, and a couple of high diesel traffic Indy stations) right now. The Exxon synergy stations are $3.94-$4.09. A 16oz squeeze bottle of Hot Shots EDT costs $17.95, or $0.045/gal. Synergy isn't worth it from the times I've tried it over other brands + Hot Shots EDT. Maybe I'd use the cheaper Exxon station if it were closer, but unfortunately only the most expensive one is somewhat in my normal paths of travel.


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## Pierre Louis (Oct 23, 2011)

alacey said:


> Well if it just as testimonial and you didn't do any scientific test with a very low margin for error, then how can you say that the scientific test used in the video with very low margin for error is wrong? It seems you are ignoring all data in order believe what you want to believe instead of looking at the facts and making an educated decision. In other words, you are letting your beliefs change the facts, and not the facts change your beliefs.
> 
> Also, the diesel fuel they were comparing it to was their own branded additized retail ASTM D975 diesel found in other branded fuel stations. They just added an additional additive(similar to how one may add an injector cleaner additive on their own vehicle) to help clean the injectors.
> 
> Lastly, this has more of an effect on modern diesels that use much higher pressures and smaller injector holes. The latest iteration of the CP4 is up to 2,700 bar, up from 1,800 bar in my 328d and 6.7L Cummins. Add that kind of pressure to smaller injector holes, and even the smallest of carbon build up could have a considerable effect on the injector spray pattern. Heck even the injector holes in my old 99 Cummins were noticeably larger than the ones on my 2014 Cummins. And yes, it did have buildup on the injector when i replaced them with performance 50 over injectors, and yes I only use branded fuel with no additives used in over three years on that engine.


Since I use branded diesel from companies arguably ahead of Exxon/Mobil in their development of retail diesel fuel, there is nothing inconsistent with my experience and the technical highlights in the video. In other words, I'm already getting the benefits of an advanced additive package, similar to what Exxon/Mobil is advertising in the video.

Cheers


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## Doug Huffman (Apr 25, 2015)

Pierre Louis said:


> Since I use branded diesel from companies arguably ahead of Exxon/Mobil in their development of retail diesel fuel, there is nothing inconsistent with my experience and the technical highlights in the video. In other words, I'm already getting the benefits of an advanced additive package, similar to what Exxon/Mobil is advertising in the video.
> 
> Cheers


Yeah, but what is your standard deviation?! More importantly what is your sample size that determines confidence level and interval? Inquiring minds want to know!

Apologies, PL, for using your post as a vehicle to express my arguably sarcastic irony.


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## alacey (Mar 14, 2018)

Pierre Louis said:


> Since I use branded diesel from companies arguably ahead of Exxon/Mobil in their development of retail diesel fuel, there is nothing inconsistent with my experience and the technical highlights in the video. In other words, I'm already getting the benefits of an advanced additive package, similar to what Exxon/Mobil is advertising in the video.
> 
> Cheers


So you have tested your current branded fuel knowing that it is ahead of Exxon's additive or is that just an assumption?

I am not saying that you are wrong in saying that other branded fuel additives like Shell FiT does the same, I am just trying to verify if what you are saying is subjective or objective. We are all allowed to have opinions on things, but opinions based on how we feel because of our bias towards/against a certain person, brand, or subject should not be construed with facts based on actual testing/verification. If it is the later then please share that information so we can all gain greater understanding and knowledge, but if it is the former then I will just take what is said with a grain of salt and move on.


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## alacey (Mar 14, 2018)

FaRKle! said:


> Around me the stations I fill up at are $3.79-$3.85/gal (76, Valero, and a couple of high diesel traffic Indy stations) right now. The Exxon synergy stations are $3.94-$4.09. A 16oz squeeze bottle of Hot Shots EDT costs $17.95, or $0.045/gal. Synergy isn't worth it from the times I've tried it over other brands + Hot Shots EDT. Maybe I'd use the cheaper Exxon station if it were closer, but unfortunately only the most expensive one is somewhat in my normal paths of travel.


Holy crap, diesel is high there.

I also agree with you. All this Synergy is is an additive that Exxon adds to the fuel before delivering it to the station. It is no different that you or anyone else adding an additional additive to their vehicle for much less.


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## alacey (Mar 14, 2018)

Doug Huffman said:


> Yeah, but what is your standard deviation?! More importantly what is your sample size that determines confidence level and interval? Inquiring minds want to know!
> 
> Apologies, PL, for using your post as a vehicle to express my arguably sarcastic irony.


Yes, it is ironic. Especially since you asked me to do the same in another article about Southwest Research doing additive testing (which I gladly did) because my word and the word of a friend that works there was not good enough. A bit of a hypocritical double standard that you would ask for verification from someone you dislike, but not expect me to ask for verification when it is from someone you like. Being an engineer I would have expected that factual data would trump bias opinions or feelings.

I can assure you that regardless of our discontent for each other, if you are right about something and back it up with factual data, I will agree with you and will not impose a double standard.


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## n1das (Jul 22, 2013)

Diesel engines lose power and efficiency over time? News to me after 17 years and over 900k miles of diesel ownership experience. With my VW TDIs years ago, power and fuel economy were still improving well past 100k miles.

At only 220k miles on my 2012 X5 35d, power and mileage are still where they should be. The car still has the original DPF (currently @ 79.99 g reported Ash loading) and has never had CBU cleaning. The HPFP and all 6 injectors are original. It is still too early to tell about any loss in power and efficiency.


Sent from my XP8800 using Tapatalk


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## alacey (Mar 14, 2018)

When I worked at Cummins, there was not one engine that did not lose some power and efficiency after our 150k mile equivalency simulation tests running standard ASTM D975 diesel(which has some additives). Mainly through the slight compression lose from carbon build up on valves and/or dirty injectors which can easily be rectified. It was only a small 1-3% of power lose for most engines which is not enough to notice in real world driving, but there were loses on every engine tested verified by and test cell engine crank dyno. I can't imagine that any other engine would not be the same over time.


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## n1das (Jul 22, 2013)

I agree, it's probably not enough of a loss for diesel owners to need to worry about. It's important to use good fuel and stay on top of all maintenance.

I haven't watched the video but has anyone compared a diesel's loss of power and efficiency over time to an equivalent gasser? Usually as gassers begin to experience weakening low end torque and increased emissions as they age, diesels are just entering their prime of life.

Sent from my XP8800 using Tapatalk


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## Pierre Louis (Oct 23, 2011)

alacey said:


> So you have tested your current branded fuel knowing that it is ahead of Exxon's additive or is that just an assumption?
> 
> I am not saying that you are wrong in saying that other branded fuel additives like Shell FiT does the same, I am just trying to verify if what you are saying is subjective or objective. We are all allowed to have opinions on things, but opinions based on how we feel because of our bias towards/against a certain person, brand, or subject should not be construed with facts based on actual testing/verification. If it is the later then please share that information so we can all gain greater understanding and knowledge, but if it is the former then I will just take what is said with a grain of salt and move on.


There is an in between. It's how we judge which brand car to buy, which spousal characteristics to choose, anything in life. With me, its also engineering information on fuel and lubricants. I have met and discussed technical topics with various oil company engineers as well as MIT material science gurus over the years, so its not easy for me to have an "opinion" not grounded in some sort of science.

Obviously you hold a grudge, which you don't hide very well.

But Exxon as a brand has not kept up with the technically savvy advertising that Shell and Chevron have with diesel over the years. They were also not producing the best fuel during the 1970's when we had the oil crisis but Shell (and Mobil BTW before they merged) did, given how sensitive my Audi 100LS was and later the early 1990's Chevy V8 single injector design that was prone to gumming up. Chevron for a long time had the single best gasoline on the market bar none. I would still favor Exxon's standing as a "top tier" fuel producer.

This video just said one thing: fuel injectors are better when clean and Exxon has the additive package that helps, without really discussing much data from a research perspective. It was a sales piece. Simple, really. But to think that diesel engines lose power over time? That is not the message, its just click bait.

Peace.


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## alacey (Mar 14, 2018)

Pierre Louis said:


> There is an in between. It's how we judge which brand car to buy, which spousal characteristics to choose, anything in life. With me, its also engineering information on fuel and lubricants. I have met and discussed technical topics with various oil company engineers as well as MIT material science gurus over the years, so its not easy for me to have an "opinion" not grounded in some sort of science.
> 
> Obviously you hold a grudge, which you don't hide very well.
> 
> ...


So your theory of which fuel is better is based on discussion rather than actual testing. Got it. I will take the opinion with a grain of salt then.

Also, I don't think diesel engines loose power over time. I know because I have seen it with my own eyes when I worked for a diesel engine manufacturer when we tested them in a crank dyno cell. Some of these reasons why they loose power, like compression loses from piston ring/cylinder wear, cannot be rectified However, some reasons, like compression lose due to carbon buildup on valves and dirty injectors, can with fuel additives either by the fuel supplier or the end user. Some of these reasons only take tens of thousands of miles while others take hundreds of thousands of miles, but it is inevitable that all engines loose power over time.

Future diesels will need higher pressures pressures and smaller nozzles to meet efficiency and emissions standards and even small amounts of build up will have more of an effect on power and efficiency. Not so much for many current or past diesels that operated under much lower pressures than 2700 bar and had much larger injector nozzles so these diesels are a mute point here.

If you want to see him go over all reasons why all combustion engines loose power in general, then you can click bait here.......

10 Reasons Why Engines Lose Power Over Time


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## Gene Horn (Mar 24, 2015)

*so what*

This is a good video to explain how an internal combustion engine works. The fact is that every internal combustion engine has deposit build up whether gas, diesel, hydrogen, or anything else. Almost all gas and diesel fuels have an additive. As far as I can tell, this test is based on fuel with no additive to fuel with the new Exxon additive. There is no comparison to anyone else's additive, no comparison between different models and makes, etc. etc. etc.

I find a difference in mileage on my V8 BMW of 5% between fill ups from different brands or even the same brand, on long distance trips. Of course, driving conditions are not identical, the full cut off at the fuel pump is different, etc. Don't forget that most fuel flows from a refinery through a pipe and is then distributed locally. It is the same base fuel between brands. The crude is not identical even from the same well nor is the refining process, even on the same day. The additives are put in at the distribution point or at the pump. That said, if you find a a mileage variation of a couple percent over repeated fill ups between brands, it is probably the difference in additives.

By the way, all engines leak a little oil into the combustion chamber through the piston rings or valve stems which increases with mileage due to wear. You saw in the video how much heavier oil is than fuel which would increase deposits when it burns. BMW V8s are notorious for valve stem leaks. That is why BMW does not consider oil usage excessive if less than a quart every 300 miles in terms of warranty! It is also why you did not have to have oil added between changes when the car was new and why you should change oil with less mileage than the 15,000 recommended.

Good luck .


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## H0ss (Sep 12, 2015)

SPL15 said:


> I always cringe at this guy's videos...


Same. I thought the title was clickbait-y when it popped into my YouTube feed, and it's working fairly well here too....


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## alacey (Mar 14, 2018)

Gene Horn said:


> This is a good video to explain how an internal combustion engine works. The fact is that every internal combustion engine has deposit build up whether gas, diesel, hydrogen, or anything else. Almost all gas and diesel fuels have an additive. As far as I can tell, this test is based on fuel with no additive to fuel with the new Exxon additive. There is no comparison to anyone else's additive, no comparison between different models and makes, etc. etc. etc.


They are comparing it to the US standard ASTM D975 which does have additives in it to bring it up to these standards. Most generic fuel stations sell this fuel without any additional additives, and most branded fuel stations add their additional proprietary additives. It is the same as an end user using ASTM D975 fuel and adding their own additional additive which would probably cost less in most cases. The only difference is when the additional additive is added, at the time of purchase from the fuel station or at the time of delivery to the fuel station.

Also, this video was sponsored by Exxon(he has other videos sponsored by various brands), so I doubt that they will pay to compare their additive to their competitors for this video. This video is free and I would probably have to pay SWRI to compare all the brand's fuel additives so I will take what I can get and not complain about it unless I was paying for it.


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## Autoputzer (Mar 16, 2014)

I usually reset my Trip Computer every time I take an outing in our BMW's. I reset the On Board Computer (OBC) MPG when I fill up the tanks. I've been tracking MPG on all my cars for over 40 years. (I was a pain in the ass before Excel.). The same trip can have the MPG vary by as much as a third.

Wind, outside temperature, traffic, random luck with traffic lights, air conditioning, passenger and cargo weight, speed, and acceleration have big effects on MPG. Wind has an effect on MPG even on a round trip, because a headwind hurts MPG more than a tailwind helps MPG. Outside temperature affects the tire pressure, about one PSI change for every 10 degrees F change in temperature, and tire pressure affects MPG.

The best OBC MPG I ever got in my 2014 535i was on the interstate, with the air conditioner blasting (August in South Carolina), with an average speed of 72.1 MPH: 30.7 MPG. I've filled up the car 147 times, and that was my only tank to break 30 OBC MPG. I did have one tank where I got 29.9 OBC MPG. The OBC decremented 0.1 MPG as I was pulling into the gas station. That was on rural highways with no air conditioning.


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## alacey (Mar 14, 2018)

I will agree there are many external variables on fuel mileage that can be rectified by slowing down or coasting more often. Some variables like wind cannot be rectified. However, this video is about internal engine variables that can effect fuel mileage & performance, and how they can be fixed. Some internal engine variables cannot be fixed so easily. Internal engine variables will generally have a more constant effect meaning it will be 2% off no matter how good or bad you drive. 

I also reset my trip computer every tank as well and record every fill-up on my aCar(Fuelly) app. My computer is generally 2-3 mpg higher than my actual calculated mileage every tank and a few times on long road trips with very little stops it has been within 1-1.5 mpg off. I also generally drive the same roads every day I drive this car since this is mainly a commuter car and I mostly drive my truck during the weekends. Sometimes I use the car during the weekends if we are going into the city, but that is seldom since I prefer to drive my truck. All I know is that I would never trust what the computers says based on the data I have collected.

If you look into my Fuelly links below(which I have purposely not synced with my phone app in a while), you will notice I put the computer's mileage in the notes of just about every fill up.


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## Autoputzer (Mar 16, 2014)

You young whipper snappers and your aps....

I've recorded my OBC MPG and calculated my "gas pump" MPG for every tank of gas I've bought since about 2004. From this data, I generate a "OBC Correction Factor (Tank), "OBC Correction Factor (Since New)," and most recently "OBC Correction Factor Since XXXXX Miles," Where actual (gas pump) MPG is OBC MPG x (1 + Cf).

Here are my "since new" Cf's:

E46 M3: -5.0%
F10 535i: +1.7%
G01 X3: -3.6% 
Chevy Cobalt SS: +0.3%

Yesterday, I had the dealership adjust the X3's MPG coefficient in the software from the default "1000" to "970." That will lower the reported MPG by 3%. I didn't have the coefficient changed to 964 because the OBC error is drifting toward 0%. You can't trust the first tank's correction factor because the car salesman might have short filled the tank to cheat you out of a few bucks. But, the 2nd, 3rd, 4th, and 5th tanks' correction factors for the X3 were: -4.8%, -5.0%, -4.8%, and -4.7%.

The dealership said that I was the first customer whose asked for the MPG display to be adjusted.

OBC error since new is not an average of the OBC errors for each tank. You have to calculate the "OBC gallons" for each tank (miles/ OBC MPG), and since new. The correction factor is equal to:

Cf (since new) = [Total Gallons (OBC) / Total Gallons (gas pump)] -1

The don't sell 91 AKI gasoline where I live. So, I blend my own from 1/3 87 AKI and 2/3's 93 AKI. This will safe me about $800 over the 100k miles I keep a BMW. Using the correction factors, I can accurately estimate the amount of fuel I'll need before I fill up the car, and how much of each AKI rating I'll need. The last tank I bought, I was off my 0.01 gallons. I'm usually within 0.1 gallons if I'm using the same pump twice in a row.

I've found gas pumps that are crooked, and some that are generous. I don't go back to the crooked ones, and they eventually recalibrate the ones that are generous. The shut-off point is different for each pump, and that affects the correction factor. But, it results in a high or low correction factor for one tank of gas, followed by a low or high one for the next tank of gas. If I get consistent correction factors from consecutive uses of the same local pump, I can accurately assess the crookedness or generosity of that gas pump.


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## Gene Horn (Mar 24, 2015)

*comments on comments*

Thanks for lots of relevant responses on this thread.

I have been told by a dealer that the BMW APG calculation is an average over several past starts unless reset. You see this if you reset while the car is rolling.


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## Autoputzer (Mar 16, 2014)

Gene Horn said:


> Thanks for lots of relevant responses on this thread.
> 
> I have been told by a dealer that the BMW APG calculation is an average over several past starts unless reset. You see this if you reset while the car is rolling.


You should assume that if any dealership employee's lips are moving they are lying. If it's not in writing, it's... not. My dealership initially told me that the MPG display wasn't adjustable. I then showed them how to do it.

The TC and OBC MPG's are calculated from the time of reset. If you don 't have your foot on the gas when resetting it, it can be unusually high right after the reset. I reset my TC MPG coasting in neutral coming out of my garage and to the end of my driveway, and it's somewhere around 25 MPG. Similarly, the instantaneous MPG will peg at 90 MPG (analog display) or 99.9 MPG (digital display) when costing at speed.

The OBC's miles remaining is calculated from the fuel tank reading (not very accurate) and the average MPG for some unknown period of time. That can be all over the place. I've see my miles remaining increase when my tank is low and I'm achieving higher MPG's than the tank's average MPG.


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## alacey (Mar 14, 2018)

Here are the differences for both my truck and car from the last time I uploaded and graphed the data in Excel a few months ago. Been recording both since my 99 3500 Cummins which was the first vehicle I owned that had a computer mileage readout. Started out as a necessity for tax reasons since I use my trucks for farm use as well as personal, and it turned into a habit. Sadly to say, out of all of my vehicles that I had over the years, these two are the most accurate.

328d








Ram 2500


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## robnitro (Aug 3, 2016)

With a consistent commute, my mpg doesn't change whether I use hotshot or not. 
I never saw improvement in my tdi either.
The additive is good to clean injectors, but it's not going to make a good running engine any better. 
The onboard idrive mpg shows within 2% usually of my trip reset miles/gals calculation.
The dash mpg I reset via bc stalk every time I go on a trip to get an idea of my mileage for that trip.


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## Pierre Louis (Oct 23, 2011)

alacey said:


> They are comparing it to the US standard ASTM D975 which does have additives in it to bring it up to these standards. Most generic fuel stations sell this fuel without any additional additives, and most branded fuel stations add their additional proprietary additives. *It is the same as an end user using ASTM D975 fuel and adding their own additional additive which would probably cost less in most cases.* The only difference is when the additional additive is added, at the time of purchase from the fuel station or at the time of delivery to the fuel station.
> 
> Also, this video was sponsored by Exxon(he has other videos sponsored by various brands), so I doubt that they will pay to compare their additive to their competitors for this video. This video is free and I would probably have to pay SWRI to compare all the brand's fuel additives so I will take what I can get and not complain about it unless I was paying for it.


Additive? What's good for the goose.....

"I am not saying that you are wrong in saying that non- branded fuel does the same, I am just trying to verify if what you are saying is subjective or objective. We are all allowed to have opinions on things, but opinions based on how we feel because of our bias towards/against a certain person, brand, or subject should not be construed with facts based on actual testing/verification. If it is the later then please share that information so we can all gain greater understanding and knowledge, but if it is the former then I will just take what is said with a grain of salt and move on."


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## alacey (Mar 14, 2018)

Pierre Louis said:


> Additive? What's good for the goose.....
> 
> "I am not saying that you are wrong in saying that non- branded fuel does the same, I am just trying to verify if what you are saying is subjective or objective. We are all allowed to have opinions on things, but opinions based on how we feel because of our bias towards/against a certain person, brand, or subject should not be construed with facts based on actual testing/verification. If it is the later then please share that information so we can all gain greater understanding and knowledge, but if it is the former then I will just take what is said with a grain of salt and move on."


I don't think you are understanding what I am saying there. Someone adding their own preferred additive (that they think is best) to regular ASTM D975 fuel or a fuel brand adding their own additive (that they think is best as well) before it gets to the station are doing the same thing since both are adding their own preferred additive. Nowhere in my post you quoted did I say which additive is best in that scenario because I have no data to back that up. I am just saying that both are adding additives to ASTM D975 fuel so go point that goose somewhere else now that you understand what I am saying.


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## Pierre Louis (Oct 23, 2011)

alacey said:


> I don't think you are understanding what I am saying there. Someone adding their own preferred additive (that they think is best) to regular ASTM D975 fuel or a fuel brand adding their own additive (that they think is best as well) before it gets to the station are doing the same thing since both are adding their own preferred additive. Nowhere in my post you quoted did I say which additive is best in that scenario because I have no data to back that up. I am just saying that both are adding additives to ASTM D975 fuel so go point that goose somewhere else now that you understand what I am saying.


Since there is no evidence that aftermarket additives even compare to those put in retail diesel, unless you have access to professional fuel analysis, your point is obviously wishful thinking.

https://www.fleetowner.com/maintenance/truth-about-fuel-additives


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## Doug Huffman (Apr 25, 2015)

Thanks, PL, for the entertaining link to an apparently internecine squabble, that included this ***8216;rebuttal***8217;.
https://www.fleetowner.com/sites/fl...012/09/Fleet Owner rebutal article 9-1-12.pdf


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## alacey (Mar 14, 2018)

Pierre Louis said:


> Since there is no evidence that aftermarket additives even compare to those put in retail diesel, unless you have access to professional fuel analysis, your point is obviously wishful thinking.
> 
> https://www.fleetowner.com/maintenance/truth-about-fuel-additives


Uhm, I am not comparing additives . I am saying that both the fuel station adding their own additive they they think is best and the end user adding the additive they think is best are doing the same thing, adding an additive to ASTM D975 fuel. I never stated one method is better than the other, but I did say that one may be less costlier. How is that so hard to understand?

Me saying that one additive is better would be strictly opinion at this point since I have no data to back it up. It is no different than your opinion about aftermarket additives since you have no data or testing backing it up either.


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## Pierre Louis (Oct 23, 2011)

alacey said:


> Uhm, I am not comparing additives . I am saying that both the fuel station adding their own additive they they think is best and the end user adding the additive they think is best are doing the same thing, adding an additive to ASTM D975 fuel. I never stated one method is better than the other, but I did say that one may be less costlier. How is that so hard to understand?
> 
> Me saying that one additive is better would be strictly opinion at this point since I have no data to back it up. It is no different than your opinion about aftermarket additives since you have no data or testing backing it up either.





> Originally Posted by alacey
> They are comparing it to the US standard ASTM D975 which does have additives in it to bring it up to these standards. Most generic fuel stations sell this fuel without any additional additives, and most branded fuel stations add their additional proprietary additives. *It is the same as an end user using ASTM D975 fuel and adding their own additional additive which would probably cost less in most cases. The only difference is when the additional additive is added, at the time of purchase from the fuel station or at the time of delivery to the fuel station. *


So which is it? Is adding your own additive to generic diesel the "same" as getting branded fuel or not?


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## alacey (Mar 14, 2018)

Pierre Louis said:


> So which is it? Is adding your own additive to generic diesel the "same" as getting branded fuel or not?


Again, you are not understanding what I was saying. What I am saying is the same there is that both are adding an additional additive. A brand fuel station adding their additive to generic ASTM D975 fuel and and an end user adding their additive to generic ASTM D975 fuel are doing the SAME thing, adding an additive. I am NOT saying one method/additive is better than another or that they are even equivalent in outcome in regards to their effects on the engine.

Maybe I should have worded what I meant better when I stated it, but then again I doubt it would make a difference since this is the third time I had to explain something that should not be that hard to understand.


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## Pierre Louis (Oct 23, 2011)

The ideal is to get the best product right away. No need to waste a perfectly nice marketing hype bottle from the additive to add to all the plastic junk in the environment. Too bad its only the pre-retail fuel that is properly modified, not the random ingredient and mostly diesel fuel, that is in the additive. There are multiple parameters that need to be met for best performance which aftermarket additives hardly begin to meet. And yes, everyone can find branded fuel like Shell diesel for less than off-brand and at a busy station no less. So there is little benefit to saying


> It is the same as an end user using ASTM D975 fuel and adding their own additional additive which would probably cost less in most cases. The only difference is when the additional additive is added, at the time of purchase from the fuel station or at the time of delivery to the fuel station.


I have no financial interest in saying any of the above except wanting my beloved diesel to live long and prosper.


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## alacey (Mar 14, 2018)

Pierre Louis said:


> The ideal is to get the best product right away. No need to waste a perfectly nice marketing hype bottle from the additive to add to all the plastic junk in the environment. Too bad its only the pre-retail fuel that is properly modified, not the random ingredient and mostly diesel fuel, that is in the additive. There are multiple parameters that need to be met for best performance which aftermarket additives hardly begin to meet. And yes, everyone can find branded fuel like Shell diesel for less than off-brand and at a busy station no less. So there is little benefit to saying
> 
> I have no financial interest in saying any of the above except wanting my beloved diesel to live long and prosper.


Again, I was not making an opinion on which was the best way to get an additive into the fuel or which additive was best since I, just like you, do not have enough supporting data (that I can present here) to say which is best and it would purely be opinion or an educated guess at best. When I said they were the same, I was referring to the fact that both methods add an additive to the standard ASTM D975 fuel, but at different points in the delivery process. The fuel brand adds an additive to the fuel the same as an end user would add their additive. Seriously, how is that hard to comprehend?


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## Arjon (Aug 5, 2019)

Bmw x1 25D lost pressure 
Hello, please anyone can help me, 
My engine is power reduced now. 
The computer read: 
Charging pressure control , control deviation
I check all the vacuum line and I don't have leaks in the tube. 
I check the EPDW (electro-pneumatic pressure converter) the vacuum in entry is -0.9 bar (its ok) i check the vacuum with hand pomp gauge in the outlet and start the engine, the pressure in outlet is 0 bar when the engine is on and when accelerate, 
I buy new EPDW and the same problem. 
Is this electrical problem? Anyone know this problem?


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