94 Octane
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MBWorld Fanatic!
Joined: Jun 2004
Posts: 1,880
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From: Seattle
05 E55
94 Octane
I usually fill up 91 at my local gas station, but the other day I noticed that they started selling 94 Octane. So, I wanted to reach out to some of you octane experts before I filled up.
My ECU is stock. I know the ECU mapping just does not give headroom for extra timing or anything above a certain octane, so is 94 okay, slightly better or potentially worse performance wise? What is the optimal octane for a stock ECU?
My ECU is stock. I know the ECU mapping just does not give headroom for extra timing or anything above a certain octane, so is 94 okay, slightly better or potentially worse performance wise? What is the optimal octane for a stock ECU?
Last edited by str8ridin; Oct 6, 2009 at 01:25 AM.
MBWorld Fanatic!
Joined: Oct 2007
Posts: 1,555
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From: Fairfax,VA
06 E55
I put 94 couple of times at Sunoco gas stations, but it is hard to find it in the area where I live. Personally I didn't feel any difference, but only put 93 octane, so a difference in 1 octane is not noticeable, home ever, when I put 91 in Pennsylvania, car was weaker. I would suggest to stick with 94 Octane, better for an engine. just my .02 cents and past experience.
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Joined: Oct 2006
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02 C32 AMG
i believe our Mercedes ECU can adapt to up to 95 octane without tuning. then after that, there wont be a benefit without a tune and then at really high octanes without a tune (109+), may actually hurt the car
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Joined: Jan 2008
Posts: 586
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From: Springfield, Missouri
03' E55 Techtite Grey
I have filled my car with 94 since I get her back into town from buying her. The car has ran strong, I don't know what it feels like with anything less really. The drive back from NC was slow and I didn't really race much. I ran the 12.0 on 94 so I don't think it hurt anything performance wise. To me I don't see any reason why you wouldn't put 94 in if it were available since our stock programming can adapt and most likely gain in performance.
Just my .02
Just my .02
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Thread Starter
MBWorld Fanatic!
Joined: Jun 2004
Posts: 1,880
Likes: 9
From: Seattle
05 E55
Well, the reason I ask about 94 is because of the following post by a very knowledgeable forum contributor:
So, that is why I posted about the 94. Maybe I'm splitting hairs with 1 octane point....
Guys, do a search for this, it's been discussed before. I've tried this with my E55 and documented it - ZERO HP gain, and the car actually runs worse on anything above ~93ish octane. The ECU mapping just does not give headroom for extra timing or anything above that octane, so it is a total waste.
Remember - the rule of thumb on octane is you want to use the LEAST amount of octane before the car detonates/preignites/etc - higher octane is harder to burn (ie, requires more ENERGY) and unless you can actually take advantage of it, will net LESS HP all factors BEING EQUAL.
Remember - the rule of thumb on octane is you want to use the LEAST amount of octane before the car detonates/preignites/etc - higher octane is harder to burn (ie, requires more ENERGY) and unless you can actually take advantage of it, will net LESS HP all factors BEING EQUAL.
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