I actually logged them at one point.. and I went from 28-29 on the highway at 91 octane to 31-32 mpg on 87 octane.

 

87 octane - I would get about 26-27 mpg with strictly hoghway driving (got 29 once). City driving with lots of stop and go I would get 18 (racetrack)/ 19-21 (shell).

93 octane - Highway gives me 31-33 mpg. City gives me 24-26 mpg.

I guess that I should also say, that in all the tests, I drove to the same places, same time, same temp,. etc.... I also drive with a slightly heavy foot and always have the AC blasting.

 

Could if possibly have something to do with where you two are located.

Steve is in wisconsin * north and cold * and

myfirstnewcar is where it is nice and warm. I am not sure at all but it could perhaps have something to do with it.

I am going to try and fill her up with highest grade possible next time then work my way back down and see how it goes