Does E46 really require 91 fuel?

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Hi all,
I dont mean to start flame in the group, but I never owned M3 before and just curious what is the common consesus for the fuel dilemma. Does usage of fuel with AKI below 91 introduce any damange to the
engine over a long run? I've owened different Acuras/Hondas (VTEC) and haven't had any problem with using gasline below 91 AKI even tho it was recommended to use 91 only.
Thanks in advance for a rational advices/responses!
-vs
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The real world answer to this is that you will see no significant difference between 91 octane and 87 octane. Newer cars have knock sensors which prevent detonation, which is why different octanes were necessary. There will be a small change in efficiency, but you will not notice it...kind of like global warming...

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Devils944S2 wrote:

What you say would be true were he talking about standard tune E46. But an M3 is not a standard tune engine. Yes, there is *some* flexibility in the timing provided. But he's driving a freekin M3 here. Pay the extra 10 cents a gallon man.
Better yet, just send me the car and I'll put the right gas in it...
--
-Fred W

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I'm in SoCal there is a 50c difference.
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Then don't drive.
If you can't afford to maintain the car properly get a donkey and cart. BMW has great cars built by great engineers whoknow what they are doing. If they say use super unleaded, this is easy, you use super unleaded.

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say Lemminings? :)
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By all means, if you feel you can garner enough internet advice to build a better car I await your production schedule. That's a highly modified high compression engine you are referring to. If you've ever tuned a carb or adjusted a distributior on such an engine your question is immediately answered. Even with the electronics, the engine will operate much more effeciently with the proper fuel. Whatever it's your car. You could likely even save some more by using cooking oil in your crankcase than that synthetic oil the other "lemmings" use on BMW's advice.

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Well said. I can never understand why anyone would want to use a fuel of lower octane than recommended. There are, clearly, lots of people about who are penny wise and pund foolish.
Bu then you also get those who (mostly) chuck money away by using a higher-than-necessary octane fuel of chaning oil much more frequently than recommended.
Folks just like to be cussed... or want something to talk about in NGs....
DAS
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Gosh... so many typos...was at end of long day and I was rushing to get home..
DAS
For direct contact replace nospam with schmetterling
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"Dori A Schmetterling" < snipped-for-privacy@nospam.co.uk> wrote in message
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snipped-for-privacy@gmail.com wrote:

between 89 and 91? You left coasters are getting the shaft! I have sen as much as 20 cents difference but most stations here it's only 10.
--
-Fred W

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SoCal gets the shaft for everthing. Tried to buy a house in OC or SD area recently?
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snipped-for-privacy@gmail.com wrote:

Nope. Wouldn't even be interested.
--
-Fred W

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snipped-for-privacy@gmail.com wrote:

Your kidding, right? Your comparing the fuel requirements of a VTEC ricer to an M3 engine?
Yes. The E46 M3 requires 91 minimum. 93 is better if you can get it.
--
-Fred W

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So what's the difference? Why S54 would have problems on low octane gasoline while. VTEC does not? I thought VTEC works in a more intensive mode ( usual RPM band 5 - 7k ) while S54 stays most of the time in mid-low RPM band (if not being raced ofcourse :) AKI is detrimantal in high RPM mode or is it closely correlated to the power curve? I hope you draw your recommendation no from what is written in the manual.
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snipped-for-privacy@gmail.com wrote:

RPM has very little to do with octane requirements.
Higher octane fuel allows higher compression and more ignition advance, thereby improving thermodynamic efficiency.
A
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snipped-for-privacy@gmail.com wrote:

The highest octane requirement occurs at the point of maximum pressure in the cylinders, and this is at the RPM where max torque is achieved. Since this engine has a relatively flat torque curve, it needs high octane all thru the middle RPM range.
Frank
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snipped-for-privacy@gmail.com wrote:

Assuming that you are replying to me...
VTEC is just Honda's method of varying the valve timing. It accomplishes the same this as VANOS in BMW engines, (but employing a different mechanism) allowing a more advanced valve timing at higher RPMs. Neither VTEC nor VANOS is the primary factor as to whether one needs to use higher octane fuel. The compression ratio and timing for the S54 engine were designed with the use of high octane fuel in mind.
Will it destroy the engine to use lower octane fuel? No... probably not.
Will the ECU adjust to compensate for the lower octane (faster burning) fuel? Yes it will (within reason).
Will you get the same engine performance burning lower octane fuel? No you will not.
Did you pay a large wad of cash for an E46 M3 (instead of a 330i or 325i) so you could then look to save 10 cents per gallon and have less than optimum performance? Only you can answer that question...
--
-Fred W

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pretty pathetic if you ask me! sell the car!
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Thanks for a good explaination, Fred. Actually, I didnt pay a large wad of cash for the car . I picked it up used for a price comparable to new Acura/Hondas. My queston stemmed from the fact that I drive at least 5 days a week in bumper-bumper 10 mph traffic therefore I dont think it will make a difference in performance under these circumstances. My only concern is if it will have any detrimental effect on engine. I didnt mean to disrespect excellent german engineering. ;)
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sell it now!
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