Anyone here running a blend of e85 to get their 91 octane fuel to 93???. Used to do this in my S4 with great success, just curious about the result in a C63S...

The ratio was about 2 gallons to every 10-12 gallons of 91...

 

Do you have before and after dyno results to illustrate the difference? Sorry, but I suspect you are wasting your time. Even if you could squeeze another couple horsepower, there would be no difference in measurable performance.

Perhaps with a highly modified engine...but then, the folks I've known doing this were mixing with proper 100+ race gas.

 

Interesting, but that's not what the tuners said. In fact, I believe if you look on the inside of the fuel door, the car should be tuned for premium??? I don't have mine yet, so cannot confirm. On the east coast, premium is 93, West coast 91.... If you check the vehicle specs, versus the manuals, e.g., torque and HP curves, you'll likely see they were all done on 93.

So, those of us with ****ty 91 would just use this method to get 93. It actually did allow me to run better numbers in my S4.

I never tracked it or did a dyno run, but it was noticeable. Further, I talked to a tuner about it.... I don't tune, but it will help on 91 Fuels supposedly in some cars.... Just unsure about the C63S....

 

By the way, the numbers to which I referred are timing numbers... I ran an obdii monitor and could log timing. I got significantly less pull, and dramatically more advance on wide open runs after adding the e85 blend.

The issue, again, it's can our fuel system handle a bit more and how did the cars run???

 

The manual in my E63 says 91 octane. I'm sure the C63 is the same. Unless you're tuning your car to take advantage of a higher octane fuel. You'll get no benefit.

By my math, your 2 gallons of E85 for 10 gallons of 91, has you past 20% ethanol. Again, read your manual, it will say not to exceed 10%.

So, in summary, you risk your fuel system (and related warranty) for dubious benefit. Why bother?

 

Ok, thanks for the info..

Interesting the vehicles are tuned for 91.
Never seen this before.