fuel mixing

[Super Unique]

Was thinking about the premium fuel requirements for our engine, and recalled that 10% ethanol is being used to eliminate MTBE in gasoline. This got me thinking about taking regular 87 octane regular unleaded and blending it with a suitable amount of e85 to yield the required 91 octane rating the car calls for. Would this then lead to running lean due to the larger amount of alcohol?

 

[hilmar2k]

You want to be really careful about running more than 10% alcohol. What is the octane rating of E85?

EDIT: Looked it up, octane is 100-104. Even still, that seems like a really bad idea to me. Assuming the octane rating is 100, then you would need 30% E85 to get to 91 octane. That puts your alcohol level at 32%, that's way too much.

EDIT #2: You do realize that your gas mileage would go down some running that much alcohol, right? Corn alcohol has about 70% of the energy as compared to gasoline. So even if it wasn't bad for your car, it might not be a good idea economically.

EDIT #3: Some further math says that running 32% alcohol would cost you a little over 2 miles per gallon assuming 25 MPG on premium gas.

 

[Super Unique]

Was just curious if anyone had messed around with the science of it. I am fine with running premium, but as prices rise some might be looking for ways to cut corners

 

[hilmar2k]

As I said in edits #2 and #3, I don't even think it is a way to cut a corner. You lose about 10% mileage. Would you even save that in fuel price? I doubt it. All around bad idea.