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  #1  
Old 12-09-2007, 05:28 AM
ssminnow ssminnow is offline
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Using regular and not premium gas

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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  #2  
Old 12-09-2007, 06:04 AM
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What does your owner's manual say?

Mine says to use Premium.

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  #3  
Old 12-09-2007, 06:25 AM
MightyY MightyY is offline
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Why would you want to retard your engine timing on purpose? Spend the extra $2/tank.
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  #4  
Old 12-09-2007, 06:27 AM
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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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  #5  
Old 12-09-2007, 06:29 AM
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Quote:
Originally Posted by wingspan View Post
What does your owner's manual say?

Mine says to use Premium.

He doesn't have a BMW owner's manual.
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  #6  
Old 12-09-2007, 06:30 AM
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Originally Posted by MightyY View Post
Why would you want to retard your engine timing on purpose? Spend the extra $2/tank.
To save $2.
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  #7  
Old 12-09-2007, 06:41 AM
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Quote:
Originally Posted by Boile View Post
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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  #8  
Old 12-09-2007, 07:10 AM
ssminnow ssminnow is offline
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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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  #9  
Old 12-09-2007, 07:19 AM
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Quote:
Originally Posted by ssminnow View Post
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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  #10  
Old 12-09-2007, 07:35 AM
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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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  #11  
Old 12-09-2007, 07:37 AM
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Quote:
Originally Posted by ssminnow View Post
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
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  #12  
Old 12-09-2007, 07:40 AM
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Quote:
Originally Posted by Fast Bob View Post
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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  #13  
Old 12-09-2007, 08:25 AM
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Should you eat canned foods all the time to save a bit of money, or should you eat fresh foods?
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  #14  
Old 12-09-2007, 08:59 AM
akhbhaat akhbhaat is offline
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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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Last edited by akhbhaat; 12-09-2007 at 09:01 AM.
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  #15  
Old 12-09-2007, 09:19 AM
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djfitter djfitter is offline
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Quote:
Originally Posted by wingspan View Post
What does your owner's manual say?

Mine says to use Premium.


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

Quote:
Originally Posted by wingspan View Post
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.

Quote:
Originally Posted by ssminnow View Post
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.
Quote:
Originally Posted by vern View Post
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.


Quote:
Originally Posted by AzNMpower32 View Post
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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  #16  
Old 12-09-2007, 09:24 AM
Boile Boile is offline
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At last. Someone that gets it.
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This post is brilliant. Completely spot on and chock full of useful information. Pure genius and original.
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  #17  
Old 12-09-2007, 10:46 AM
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jcatral14 jcatral14 is offline
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Quote:
Originally Posted by akhbhaat View Post
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?
Excellent, excellent post. You should save this in a Word document to paste in future threads like this

And yes, I do shampoo, rinse and repeat
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  #18  
Old 12-09-2007, 10:54 AM
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MMME30W MMME30W is offline
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Quote:
Originally Posted by djfitter View Post
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.





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.




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
Quote:
Originally Posted by Boile View Post
At last. Someone that gets it.
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/sho...remium+regular

http://www.bimmerfest.com/forums/sho...remium+regular

http://www.bimmerfest.com/forums/sho...remium+regular

http://www.bimmerfest.com/forums/sho...remium+regular

http://www.bimmerfest.com/forums/sho...remium+regular

http://www.bimmerfest.com/forums/sho...remium+regular

http://www.bimmerfest.com/forums/sho...remium+regular
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  #19  
Old 12-09-2007, 11:10 AM
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We don't want to waste time researching so we can spend more time watching football.
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  #20  
Old 12-09-2007, 11:28 AM
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MMME30W MMME30W is offline
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We don't want to waste time researching so we can spend more time watching football.
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/sho...9&postcount=21
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Old 12-09-2007, 11:35 AM
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Originally Posted by wingspan View Post
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/sho...9&postcount=21
I'll be doing my brakes in 3K miles.
I started looking at prices online and pretty soon I remembered why last time I bought my discs from the dealer. Those things are heavy and after you figure out shipping, dealer is only $5 more. Brake pads, yes, buy online and get the Axxis Deluxe or Ultimate.
If I were to do anything non-OEM it'd be for looks, not performance.
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  #22  
Old 12-09-2007, 12:22 PM
Valley320i Valley320i is offline
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I'm in Nova Scotia. On a couple of cold mornings my Canadian 04 320i took a couple of trys to get started. The dealer told me they had a technical bulletin for just the 320i recommending running a couple of tanks of 87 octane (regular) to "reset" the anti-knock sensor. I'm on my fourth or fifth tank of regular and have noticed no difference in fuel economy or performance. The only difference I've noticed is the car hasn't had any more issues cold starting. I'm sure this must have everything to do with the lower detonation point on the regular. Anyway I've been hesitating going back to the premium. Based on the mileage I put on the car and the price of gas here I'm looking at an extra $500 dollars or so a year for the premium fuel. I probably will go back to premium simply because I've always taken care of my vehicles and followed the manufacturer's recommendations. It's resulted in years of worry free driving for me...so why stop now.
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  #23  
Old 12-09-2007, 12:35 PM
ktc ktc is offline
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I'll be doing my brakes in 3K miles.
I started looking at prices online and pretty soon I remembered why last time I bought my discs from the dealer. Those things are heavy and after you figure out shipping, dealer is only $5 more. Brake pads, yes, buy online and get the Axxis Deluxe or Ultimate.
If I were to do anything non-OEM it'd be for looks, not performance.
We're in the same boat. I wouldn't mind having colored calipers
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  #24  
Old 12-09-2007, 01:37 PM
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Like akhbhaat said Why would you want to drive with reduced power and fuel economy. Why would you want to risk potentially damaging or destroying your engine to save $2.00 a tank? To me that just doesnt make sense. If you can afford a BMW shouldnt you just not worry about an extra $2-4 a week ?
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  #25  
Old 12-09-2007, 04:00 PM
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Quote:
Originally Posted by Boile View Post
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.
+1 - and driving 15k miles per year, getting only 21 average mpg, premium gas only costs about $200 more annually if the price difference is 30 cents per gallon.
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