I was wondering which has better mpg for my b18c1, before I ran 89 octane and it was bad, so I started running 92 with 10 ethanol and noticed that my gas goes down more than the 89, I was planning to use 92 without ethanol, but I want to see what you all think about this.

 

WTF does "goes down more" mean?

 

Sorry for my pidgin language... I meant it eats more than the 89.

 

I hope this is a trolling post.

But just in case it isn't. You have an engine that mandates 91 minimum octane, and you decided to run 89 in it? Gas mileage is the least of your concerns while doing this...

Ignoring that, without a retune, your mileage should be the same for 92 with and without ethanol. With a proper tune for the fuel, obviously the mileage will be worse for E10, but without it the correction for the ethanol won't make any real difference, you'll just run slightly lean.

Your driving habits will make more of a difference in mileage than the fuel.

Stoich for ethanol is 9:1. Stoich for gas is 14.7:1.

 

I don't understand why you're even asking. If you have both available then run a tank of one, then a tank of the other and compare.

And doesn't that engine take "Premium Fuel Only"?