I consistently get 28-29 mpg running Sunoco 93. Tried their 91 octane as an experiment and lost 1 maybe 1.5 mpg and noticed the power wasn't quite the same, throttle seemed a little "slow", no audible knocking or pinging,but the car ran like the crossfire I had when living in AZ- 4600' elevation may have been a factor there, but the highest availible octae was 91 (latern fuel as far as I'm concerned). Anyway, the 2 cents per gallon difference isn't worth the mpg and performance penalty.