I decided not long ago in my search for higher mpg to mix up 87 octane with 91 octane and rather then just running the tank with 87 down to like 10 percent, I ran it to 50 and then filled it to full with 91 and repeated did that till I had 91 octane almost I believe. Needless to say my mpg WENT DOWN!!

So for whatever reason I decided to put in 100 octane in my 91/87 octane mix, and I dont think it liked it either.... So what in theory could I have screwed up? The knock sensor maybe? What typically needs to be replaced or done to undo the effects of mixing octane ratings? Help me get my mpg back up!

 

This is normal. It's a misconception that higher octane gas provides higher mileage. The energy content of higher octane gas is LOWER than 87.


In the vast majority of cases where high octane fuel is not required, mpg goes down when high octane gas is used where 87 is specified.


You didn't screw up anything except hurt your wallet. Simply fill with 87 from this point forward.