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Discussion Starter #1
I had a 997 C2 which was flashed for 94 and I mixed 91 and 100 on a regular basis. I currently run a mixture and sometimes a full tank of 100 in my non-flashed M5. Does anyone else have any experience in higher octane fuels in their US E60 M5? If so, do you feel the difference in the power or just you wallet? :M5rev:
 

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Back in the day it was 5.99 at this station about 10 miles from my house. I filled up all the time at that price.

Now I'd be lucky to find it somewhere for less than 8 or 9 bucks.
 

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100 octane wo/alcohol...in my opinion is really not needed....
.
A good quality fuel like Shell is more than enough...
 

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Back in the day it was 5.99 at this station about 10 miles from my house. I filled up all the time at that price.

Now I'd be lucky to find it somewhere for less than 8 or 9 bucks.
Actually, in my experience, the delta between Premium "Pump" gas and 100 octane is now that high. IIRC, 100 OCtane is still in the $6.XX/gallon range, which ain't bad compared to ~$4/gallon premium. Not sure why this is the case-- maybe they sell so little of the stuff that they are pricing it off of the last truckload of the stuff from six months ago.

In the M5, I felt like the 100 octane stuff helped the car pull a little harder on hot track days, but could have been placebo.

In 997TT with 100 octane ECU Program, the difference is huge.

For street driving in M5, 100 octane is a waste for sure.

-Chris
 

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A couple of months ago here in the bay area, a few friends and I went out for a play date with our cars. On my way to meeting up with everyone, I stopped by Sears Point and picked up some 100 octane. (second tank actually. Was on business the previous day and filled up with it also) So my tank was completely 100 octane. I think It was about $7 a gallon.

Let me start by saying, the engine idled much better with the 100 (sound and smoothness). I was impressed. Now, I have read posts on this forum before about loosing power, or feeling like it is loosing power with 100, but you need to take into account the ignition will change itself to give more spark into the combustion chamber because the gas will not ignite as easily. This will translate into you having to push on the gas peddle further for more air to get into the engine. This is where I feel people think they are loosing power because it might not feel as "peppy", but you are putting more air and gas into the combustion chamber, which will make the engine stronger.

The sound when running on 100 is also better. It sounds "throatier".

You may like the 100 octane, or you may not. I sure do, but only fill up on certain occasions. I don't think its worth putting in your car everyday if you commute in it, although you gas mileage will increase substantially. But the cost is not worth the gain in mileage. But worth the fun on those play days!!


Eric
 

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Discussion Starter #8
Checkout this post by Toan.

http://www.m5board.com/vbulletin/showpost.php?p=1257332&postcount=27

My experience is that it really doesn't improve anything. I have Powerchip
software so maybe that's why?
These appear to be mapped ECU's which have all error correction of different octanes written out of the program (ie, will not take advantage of high octane fuel). I am referring to non-mapped cars which should adjust the timing based on fuel (to a point). I think my M5 idols better and is smoother with race fuel (but, it could just be in my head) and the high compression ought to take advantage of the change in octane. It's not that expensive here in Scottsdale (~$6.70-$6.90) so I fill it every third tank or so (no rhyme or reason)
 

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Wonder if anyone from Germany could contact M directly and ask them what is the optimum octane this car can have to get the most from the engine and stock ECU?
 

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Discussion Starter #11
IMO, in order to benefit from race gas, ecu need to advance timing more to accomodate that. Race gas with stock ecu, I think it's a waste.
I think your right. The fuel door does state a fuel range of 91-95 US. Maybe I should stick with 91 (though in AZ our fuel is on the low end of quality).
 

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In most cars, a higher octane is not going to do anything unless you have the car tuned for it. I'm not 100% sure with the M5, but I know that most cars are like that.
 
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