# More frequent oil changes......possibly less carbon buildup?



## totitan (May 11, 2013)

A friend of mine has been a master BMW mechanic for 25+ years. He spent 15 years working at dealerships and for the last 10 years as an independent BMW shop. Now that I own a BMW again I took the d over to show him and pick his brain about carbon, atf changes, oil, etc. Once a year he gets together with other BMW mechanics fromall over for the latest training and updates. Regarding the carbon buildup issue, he said it was widely discussed and debated this year. The consensus was that increasing the frequency of oil changes to 7500 miles results in much less carbon build up. He said the level of contaminates in the oil is directly related the amount of carbon buildup that occurs. He also said that the engineers are aware of this but changing the frequency of service is verbotten by marketing/management for obvious reasons.

Regarding oil he likes total/elf the best.

Regarding atf service he said to do it every 60K or not at all. Waiting till 100K is not good.

Since he was nice enough to allow me to take up his valuble time I though I might as well share with you guys. If you dont like what he said just disregard it but please dont attack me for sharing.


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## Ilovemycar (Feb 19, 2010)

Hi, I just subscribed to this thread in order to bookmark this (I'm very rarely in this subforum), and my subscription folder had been empty for a long time now. I find what your friend said to be very interesting, but a quick question: was he referring to all BMW engines, a certain subset of them, or are you guys talking very specifically about BMW diesels only in this case? Thanks. (I know it's the diesel forum, but I need to ask!) :angel:


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## totitan (May 11, 2013)

He works on BMW only so this applies to BMW direct injection engines gas and/or diesel. Port injection motors do not have the problem


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## Ilovemycar (Feb 19, 2010)

totitan said:


> He works on BMW only so this applies to BMW direct injection engines gas and/or diesel. Port injection motors do not have the problem


Thanks!


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## montr (Oct 7, 2006)

I change the oil in between scheduled oil change, i.e. change every ~6000 miles. That did not prevent me having problems with multiples injector change. I do no know if I have carbon built-up as this has not been authorized by BMW


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## d geek (Nov 26, 2008)

totitan said:


> A friend of mine has been a master BMW mechanic for 25+ years. He spent 15 years working at dealerships and for the last 10 years as an independent BMW shop. Now that I own a BMW again I took the d over to show him and pick his brain about carbon, atf changes, oil, etc. Once a year he gets together with other BMW mechanics fromall over for the latest training and updates. Regarding the carbon buildup issue, he said it was widely discussed and debated this year. The consensus was that increasing the frequency of oil changes to 7500 miles results in much less carbon build up. He said the level of contaminates in the oil is directly related the amount of carbon buildup that occurs. He also said that the engineers are aware of this but changing the frequency of service is verbotten by marketing/management for obvious reasons.
> 
> Regarding oil he likes total/elf the best.
> 
> ...


So a bunch of guys who make money servicing cars (oil changes included), came to the conclusion that changing the oil reduces carbon build up? Interesting. Please ask your friend to explain how the oil will lead to carbon build up.

What goes on in the combustion chamber should not be affected by the the oil. If the oil is doing its job and the engine is tight then very little oil will be burnt. The carbon build up in a diesel is mainly due to EGR. Oil analysis will tell you if the oil is breaking down and I think there is an oil analysis thread on this subforum that indicates 10k oil changes are OK in some cars. If I had any question I'd get my own oil analyses done- maybe at 5k, 7.5k and 10k on the oil and make my own decision on when to change the oil based on my car and my driving habits.


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## totitan (May 11, 2013)

First of all the carbon buildup occurs in the intake manifold and intake side of the head, not in the combustion chamber, so most of your points are not applicable to carbon buildup. Secondly some misting of the oil is created by the egr system. Said oil mist is then sent down the intake manifold and by the intake valves. Oil as we all know, holds contaminants in suspension until is drained and replaced by clean oil. The theory is that it is the contaminates in the oil mist that are causing the carbon and not the oil itself. It makes sense to me so I'm going to change my oil more frequently and see what happens.


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## Flyingman (Sep 13, 2009)

I'm not really buying into this theory that it is from the oil.

Our engines use so little oil that it would be difficult to justify the carbon buildup is coming from the oil.

If the oil had so much contaminants in it, we would see those in our multitude of oil analyses posted on this site. I've been doing same for the past 9k miles, every 4,000 miles, and you can see for yourself what are the contaminants in the oil.

The additive package remains almost untouched, so it's not coming from the additives. No signs of any degradation of the oil but some slight deterioration of the TBN, as to be expected as it is combating the sulfur from the fuel.

There is some iron, aluminum and other wear metals present.

I would suggest that 99% of the sludge that is built up in the intake is organic matter from incomplete combustion of fuel. This is coming from the EGR recycling and I suspect from valve overlap when both intake and exhaust valves are open and some small amount of back pressure from exhaust is being blown back into the intake. But that is merely a guess on my part.

Changing the lube oil won't harm anything but I doubt it will have any impact on the carbon build up in our intakes.


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## AutoUnion (Apr 11, 2005)

That sounds like a bunch of crap to me. He just wants to make more money off you. 

Lexus has been running 5k intervals on their cars and on the ones without their D4-S dual injection system, carbon buildup is still an issue. This would be with the IS250. The IS350's V6 has the dual injection system and have zero issues.

Same thing with Audi. They run a smaller interval than BMW and they still have problems. GM does with their EcoTecs and they also run a smaller interval than BMW.


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## F32Fleet (Jul 14, 2010)

Interesting. So your buddy is saying that the design of the head can't even handle a minimum amount of oxidized oil. 

I still think it's a combination of out of spec diesel which is causing injector fouling and therefore poor burn in addition to low speed driving. 


I guess I'll stick to the 7.5k mile OCI.

You should ask you tech about Lubro-Moly Diesel Intake Cleaner.


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## UncleJ (May 7, 2006)

Don't know about the carbon build up because of extended oil change intervals, but it can't hurt to change oil early. What it may well do is help in the case of bio diesel contamination in the sump! Mazda has experienced some problems in this area with their new diesels and has found that increased change intervals alleviate this problem to a significant degree. Our friends in Oz have commented on this, since we can't get those Sky-Active diesels here yet. I think the new recommended oil change interval may be 5K miles, but may be wrong.:angel:


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## txagbmw (Apr 15, 2013)

On old diesels. There was a very noticeable difference in oils. You could take a 3,000 mile gas oil and still look clean with a 3,000 diesel oil being pitch black.
The diesel oil would even stain the concrete if spilled. This is diesel from the 80's. If diesel oil still does this can see where a problem would occur if ? misted
back into the intake


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## AutoUnion (Apr 11, 2005)

txagbmw said:


> On old diesels. There was a very noticeable difference in oils. You could take a 3,000 mile gas oil and still look clean with a 3,000 diesel oil being pitch black.
> The diesel oil would even stain the concrete if spilled. This is diesel from the 80's. If diesel oil still does this can see where a problem would occur if ? misted
> back into the intake


The oil turns black almost immediately after an oil change on a modern diesel too.

- Sent from Galaxy S4


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## Hoooper (Jun 17, 2013)

txagbmw said:


> On old diesels. There was a very noticeable difference in oils. You could take a 3,000 mile gas oil and still look clean with a 3,000 diesel oil being pitch black.
> The diesel oil would even stain the concrete if spilled. This is diesel from the 80's. If diesel oil still does this can see where a problem would occur if ? misted
> back into the intake


oil in our motors is pitch black from the day its changed, thats just a fact of diesel life. I dont think that makes a significant difference though, its just soot which is the same thing recircing through the EGR, so you get some minimal amount of soot already in the oil combining with a bunch of soot coming through the EGR. Gas engines dont get this because they dont create soot in the same manner as a diesel.

Your friends experience is most likely a result of gas engines, which he is saying is the same as the build up we have on our diesels because they both use direct injection, but our issues are fairly different from those of the gassers


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## d geek (Nov 26, 2008)

totitan said:


> First of all the carbon buildup occurs in the intake manifold and intake side of the head, not in the combustion chamber, so most of your points are not applicable to carbon buildup. Secondly some misting of the oil is created by the egr system. Said oil mist is then sent down the intake manifold and by the intake valves.....


Oil vapor will be present from crankcase fumes, but not from the EGR. The latter is only exhaust gas, which will be full of soot because it is upstream of the DPF. the oil vapor and soot may combine to make a nasty mess. Older VW diesels were plagued with this combination and resultant intake clogging. The heat (coming from the combustion chamber) contributes to the problem.


totitan said:


> ... Oil as we all know, holds contaminants in suspension until is drained and replaced by clean oil. The theory is that it is the contaminates in the oil mist that are causing the carbon and not the oil itself. It makes sense to me so I'm going to change my oil more frequently and see what happens.


Still doesn't make any sense that changing the oil sooner will somehow prevent this buildup from happening. Advice to VW owners was always to drive the car hard because the EGR rate is cut back when you do.

The oil is designed to hold soot in suspension for at least 10k mi. If your car is modded you should probably change it earlier because the soot can buildup quicker when you add more fuel.


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## totitan (May 11, 2013)

AutoUnion said:


> That sounds like a bunch of crap to me. He just wants to make more money off you.
> 
> Lexus has been running 5k intervals on their cars and on the ones without their D4-S dual injection system, carbon buildup is still an issue. This would be with the IS250. The IS350's V6 has the dual injection system and have zero issues.
> 
> Same thing with Audi. They run a smaller interval than BMW and they still have problems. GM does with their EcoTecs and they also run a smaller interval than BMW.


 He's not trying to make money off me. He knows that I change my own oil. I went to him for his opinion on three specific things, Nothing more nothing less


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## ssbourbon (Sep 1, 2013)

not that I have a BMW diesel yet, but, I have had a 2000 Jetta TDI for 9 years now...just rolled over 410,000 miles yesterday. Many have had their intakes clog, I never have, last timing belt change I looked in and it just had a thin covering of carbon in there.

So what does this mean? It means that I drive a lot of highway miles, the engine gets to and stays at operating temp, keeps the intake drier and allows more burn off internally, thus keeping it clean. Seems that the clogged ones aren't run but locally and the stuff inside is kind of a really hard sludge.

Oil changes don't impact clogging of the intake to the best f my knowledge, but how the car is used certainly will. I have been at a 10K OCI for all of these years and the engine is stock, thankfully all original, even the turbo, just rebuilt injectors and injection pump at 360K because they just needed it.

Food for thought, i'd like to see what the drivers here feel about or have experienced in that manner...City drivers chime in...Highway drivers chime in...Any differences? I would really like to know.

Scott


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## totitan (May 11, 2013)

ssbourbon said:


> not that I have a BMW diesel yet, but, I have had a 2000 Jetta TDI for 9 years now...just rolled over 410,000 miles yesterday. Many have had their intakes clog, I never have, last timing belt change I looked in and it just had a thin covering of carbon in there.
> 
> So what does this mean? It means that I drive a lot of highway miles, the engine gets to and stays at operating temp, keeps the intake drier and allows more burn off internally, thus keeping it clean. Seems that the clogged ones aren't run but locally and the stuff inside is kind of a really hard sludge.
> 
> ...


Thanks for your input. The longevity of your VW diesel is good to know, as I have one too....a 2012 JSW TDI. There has been some members here that have driven mostly highway miles and have still had carbon buildup issues. This is what motivated me to quiz the guy I know who has worked on nothing but BMW's for 20+ years, and has had all their specialized training. Who knows what the solution really is, but Im going to keep searching for it.


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## Flyingman (Sep 13, 2009)

Diesel engines are definitely designed for the long haul type of service. Idle and partial load (20-30%) will definitely carbon them up.

I have 60+K now with 13k OCI. I commute 72 miles round trip and at least 60% of that distance is highway at 80mph +-.

If engine is running at load, with turbos spooled up you have good positive boost and I think this helps keep intake clean and exhaust from backing up during valve overlap.

Ohh, and no carbon build up to the best of my knowledge!


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## m6pwr (Jan 26, 2008)

I think the BMW mechanic may have been referring to a well known problem that afflicted the then new direct injection gasoline engines that were turbo-charged. The high heat of these engines (operating oil temps at or above 250 degrees F) and the absence of detergent fuel washing the intake valves (since the injectors were now in the cylinder) led to oily vapors depositing carbon in the intake tract. That eventually led to rough running and loss of power. The oily vapors were drawn up into the intake tract largely through the crankcase ventilation system. To my knowledge, it was restricted to the gas direct injection engines and not diesels. It was a big problem at one time with some of the turbo Audis. Early BMWs with the N54 engine (e.g. 335i's, etc) suffered too, as well as some of the Mini's. BMW completely redesigned the ccv system when the the N55 successor engine came out, I think to deal with the problem. Some of the oil companies also have also formulated oils that have much higher resistance to volatilization and giving off vapors (expressed in technical terms as the NOACK number - - the lower, the better). Probably the best example of one of these low NOACK oils is Pennzoil Ultra 5w40 Euro oil (it's rated BMW LL01 if you have a a gasser).


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