I just put in my 1st tank of 91 and we'll see what the premium experiment returns. Immediatly I did notice my miles til empty was 305 when it has never read above 295 previously with 85 and that was with just a 1 mile drive home from the station.
I'm,of course,going to figure it on paper also but I'm starting with an indicated 26.4mpg and a real 29.4mpg on paper with all city driving and nearly 100% with the AC on.
'12 Focus Red Candy SE Sport 5 spd
'99 Toyota 4Runner Sport
'11 Subaru WRX STI Hatch