# Using regular and not premium gas



## ssminnow (Dec 4, 2007)

So somebody told me that it is fine to use regular gas in a BMW. They said that the computer would compensate for the lower octane by changing the timing and it is a waste of money. 

Does anyone know if there is any truth to this? Real evidence not just someone saying it is a stupid thing to do and why would you want to do that.

Thanks!


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## Rich_Jenkins (Jul 12, 2003)

What does your owner's manual say?

Mine says to use Premium.

: popcorn:


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## MightyY (May 21, 2007)

Why would you want to retard your engine timing on purpose? Spend the extra $2/tank.


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## uncle ken (Feb 3, 2007)

When you use 87 octane your knock sensors will retard the ignition advance in an effort to avoid engine damage. Of course the engine has to ping a few times before the knock sensors function...or you could just do what BMW recommends. If you are determined to pump regular grade gasoline be sure and add a Turbonator to compensate for any power loss!

http://www.turbonator.com/index.html


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## Boile (Jul 5, 2005)

wingspan said:


> What does your owner's manual say?
> 
> Mine says to use Premium.
> 
> : popcorn:


He doesn't have a BMW owner's manual.


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## Boile (Jul 5, 2005)

MightyY said:


> Why would you want to retard your engine timing on purpose? Spend the extra $2/tank.


To save $2.


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## Rich_Jenkins (Jul 12, 2003)

Boile said:


> He doesn't have a BMW owner's manual.


I'm not 100% sure. Why would someone come onto a BMW forum and ask a question like that without a BMW?

Sorry, I was distracted by the football game I was watching on TV.


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## ssminnow (Dec 4, 2007)

First off, it was merely a question. My shampoo instructions says to wash, rinse and rewash. I dont do that either. I am sure you do though.


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## Fast Bob (Jun 4, 2004)

ssminnow said:


> First off, it was merely a question. My shampoo instructions says to wash, rinse and rewash. I dont do that either. I am sure you do though.


BMW engines are high compression, high-performance machines, and require premium fuel to perform at their maximum potential.

Regards,
Bob


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## ktc (Jan 10, 2005)

I'm going to assume that if you can find the low-grade enough gas, there isn't anything the engine timing can do to prevent the fuel from just auto-combusting... I would hate to have to clean up that engine afterwards. Talk about a good way to reduce longevity.

Aside from octane, I would try and use top-tier fuel as much as possible. I plan on keeping my car for at least 5+ more years, and the thought of all that junk accumulating and slowly impairing the engine is just sad.

YMMV.


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## vern (Apr 19, 2002)

ssminnow said:


> First off, it was merely a question. My shampoo instructions says to wash, rinse and rewash. I dont do that either. I am sure you do though.


Very bad cmpareison unless you got pistons on your head. just do what BMW recomends and use premium gas and you will be doing the right thing without engine problems down the line. If you want tons of information on the subject do a SEARCH, the subject matter has been beaten to death. Good luck
cheers
vern


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## Boile (Jul 5, 2005)

Fast Bob said:


> BMW engines are high compression, high-performance machines, and require premium fuel to perform at their maximum potential.
> 
> Regards,
> Bob


But that doesn't answer his question.
Will the engine self-compensate for the lower octane gas? YES.
Is it a waste of money to use high octane gas? NO. You get lower mileage per gallon with low octane gas, so you end up losing more than $2 per tank.


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## AzNMpower32 (Oct 23, 2005)

Should you eat canned foods all the time to save a bit of money, or should you eat fresh foods?


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## akhbhaat (Apr 29, 2003)

The short answer is: it is _technically_ acceptable to use "regular" (lower octane) fuel in a BMW.

To understand why, you must know why BMW recommends high octane fuel in the first place. To avoid writing a novella, I'm going to assume that whoever reads this has some fundamental grasp of physics and chemistry.

Octane rating is a measure of the gasoline's resistance to detonation. Note that octane itself is a hydrocarbon atom (not unlike butane, heptane, propane and so forth). This is an important measure because gasoline is a relatively volatile substance. If you increase the pressure or temperature inside the cylinder, you increase the likelihood that the fuel will detonate before the spark plug fires (uncontrolled detonation/engine knock). Uncontrolled detonation can obviously cause serious damage to the engine.

Most of BMW's engines run relatively high compression ratios, which for our purposes is essentially akin to saying that they operate with high cylinder pressures. By running lower octane fuel with the factory specified compression ratio and ignition timings, you run a high risk of uncontrolled detonation. Of course, knowing that the average consumer is an idiot or that high octane fuel may not be available in all regions, BMW has installed knock sensors to adjust the engine's ignition timings if they detect conditions that would lead to premature detonation.

Thus, it is "safe" to run 87 octane in the car (I knew a friend who did just this for years in his 528i). However, this comes at the price of reduced fuel economy and power because the remapped timings are not as efficient as the factory defaults, obviously. And just be aware that if a knock sensor fails (given the failure rate of sensors in German cars, it's a valid concern), you could be in a spot of trouble.

At current fuel prices, the difference in price between 93 octane and 87 octane is less than 7%. If you don't mind losing power and fuel efficiency (which will actually mitigate some of the cost savings) and implicitly trust your engine's knock sensors, then by all means - run 87. But if 2 or 3 dollars per 50 dollar tank is of any concern to you, perhaps you bought the wrong car?


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## djfitter (Sep 12, 2007)

wingspan said:


> What does your owner's manual say?
> 
> Mine says to use Premium.
> 
> : popcorn:


His post of a few days ago says he is going in for negotiations and hasn't purchased yet, so no Owners Manual.



wingspan said:


> I'm not 100% sure. Why would someone come onto a BMW forum and ask a question like that without a BMW?
> 
> Sorry, I was distracted by the football game I was watching on TV.


Maybe so he can figure the cost of ownership.



ssminnow said:


> First off, it was merely a question. My shampoo instructions says to wash, rinse and rewash. I dont do that either. I am sure you do though.





vern said:


> Very bad cmpareison unless you got pistons on your head. just do what BMW recomends and use premium gas and you will be doing the right thing without engine problems down the line. If you want tons of information on the subject do a SEARCH, the subject matter has been beaten to death. Good luck
> cheers
> vern


He made an analogy not a comparison. The IDEA of whether to blindly follow the instructions given is what was in question not if he shampoos his pistons on his head.



AzNMpower32 said:


> Should you eat canned foods all the time to save a bit of money, or should you eat fresh foods?


Again, another comparison that has nothing to do with the original question.

At least Boile and ahkbhatt offered up some kind of pertinent information.

dj


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## Boile (Jul 5, 2005)

At last. Someone that gets it. :thumbup:


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## jcatral14 (Aug 4, 2003)

akhbhaat said:


> The short answer is: it is _technically_ acceptable to use "regular" (lower octane) fuel in a BMW.
> 
> To understand why, you must know why BMW recommends high octane fuel in the first place. To avoid writing a novella, I'm going to assume that whoever reads this has some fundamental grasp of physics and chemistry.
> 
> ...


Excellent, excellent post. You should save this in a Word document to paste in future threads like this :rofl:

And yes, I do shampoo, rinse and repeat


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## Rich_Jenkins (Jul 12, 2003)

djfitter said:


> His post of a few days ago says he is going in for negotiations and hasn't purchased yet, so no Owners Manual.
> 
> Maybe so he can figure the cost of ownership.
> 
> ...





Boile said:


> At last. Someone that gets it. :thumbup:


You make some good points. I just thought it was a strange question, that frankly could be answered in a few minutes by a google search, or by searching this board. Perhaps people are more interested in starting a new conversation on a topic these days, then taking a few moments to research the issue for themselves.

I thought providing a comment relating to the fact that the OEM in my case recommends premium fuel was pertinent information. Excuse me.

To the OP - Good luck with your question. Here is some additional information you might want to check out:

http://www.bimmerfest.com/forums/showthread.php?t=184859&highlight=premium+regular

http://www.bimmerfest.com/forums/showthread.php?t=141783&highlight=premium+regular

http://www.bimmerfest.com/forums/showthread.php?t=101793&highlight=premium+regular

http://www.bimmerfest.com/forums/showthread.php?t=110001&highlight=premium+regular

http://www.bimmerfest.com/forums/showthread.php?t=101793&highlight=premium+regular

http://www.bimmerfest.com/forums/showthread.php?t=55737&highlight=premium+regular

http://www.bimmerfest.com/forums/showthread.php?t=8836&highlight=premium+regular


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## Boile (Jul 5, 2005)

We don't want to waste time researching so we can spend more time watching football.


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## Rich_Jenkins (Jul 12, 2003)

Boile said:


> We don't want to waste time researching so we can spend more time watching football.


:rofl: True, that.

Did you ever come back on the brake thread? Apols if I missed it. I was interested if anyone was planning on using the BMW Performance rotors...I think I'll just stick with OEM rotors and pads (my first E46 brake job, 44K miles) this time around, but those performance rotors do look cool...

NM, got it: http://www.bimmerfest.com/forums/showpost.php?p=2851949&postcount=21


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