E85 mix with 93 octane

Old 10-04-2012, 08:56 AM
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C250 Coupe, SL 500, Audi A8L, 360 Spider, Bentley
E85 mix with 93 octane

Today i'm mixing my tank 60/40 93/E85 has anyone done this? Hoping tosee power gains my local tuning shop said i would see gains and i trust them.
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Old 10-05-2012, 08:12 PM
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2012 C250 Coupe
I'm 99.99% sure the C250 can't run on E85 fuel... The only W204 model that previously could take advantage of E85 "Flex Fuels" was the C300 sedan 2008-2011. However, this is not applicable on 4matic models, and only pertained to RWD models. I am not sure that the 2013+ models retain this felxibility, as it is a different engine. Furthermore, E85 certainly does not provide more power or efficiency, if anything it is more sluggish, dirtier and less fuel economy. Additionally, you should NEVER mix regular fuel and e85 (on cars that support it); it is recommended you run the tank near empty and switch fuel type entirely.

I'm sorry, but ditch your local "tuning shop" they have no idea what they are talking about - and if you already added E85 fuel to your tank, ask if they will cover the cost to get your tank pumped empty... If you see this message before you fill up or mix your car - DON'T DO IT! If you have done it and your car is still miraculously still runs - cease use immediately and have your fuel system flushed.

Last edited by jctevere; 10-05-2012 at 08:20 PM.
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Old 10-18-2012, 01:31 PM
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I'm late to the party here but do NOT mix them that much.

E85 has an entire different stoichometric ratio than pump fuel does.

Also, E85 has less energy per volume than pump fuel, meaning you will NOT make more power just by using it and you will lose fuel economy. The reason people are able to use E85 and make more power is because of it's higher latency to resist pre-detonation, meaning that you can use more boost (on a boosted car at least) and run a more aggressive timing map.

If they are telling you that you can just pump E85 in it and go, they are very very wrong.
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Old 11-16-2012, 12:40 PM
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Just wondering what ever came of this? I will say I have tested e85 on several cars (mainly rental cars). I never had a problem, except on two pf the cars I got a lean code. However, the light went off once I filled back up with regular gas. If you have the turbo model C250 you could make power gains on the e85. The issue though will be the ability of the Fuel Pump and Fuel injectors to keep up with the higher flow rate of e85. This may be why the shop said to blend the two fuels. I've heard mixed stuff about how they mix together in the gas tank. But being e85 is 15% gas, I'm sure it has to in some way. Personally I have converted a supercharged car that I have to e85 (I did change out my fuel pump and injectors though). My power went up about 40whp and 70wtq. This was on a Pontiac though, not a Mercedez so the systems may be very different?
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