Quote Originally Posted by 34_40 View Post
...Also, gas with a lower octane number doesn't mean it's of a lower "quality", but it does burn quicker for a shorter power cycle. And many vehicles actually achieve a better mpg on a lesser octane rated fuel!
I agree 100%. I took a class in college, Internal Combustion Engines, and one of the things we learned was that at a given timing setting you get the most power and highest efficiency with the lowest octane fuel that your engine tolerates without any pre-ignition "ping", and to clarify, "ping" precedes "knock" which is detonation. Back in the day when we had only two grades, "regular" and "ethyl", guys would pull in and say they were going to fill up with ethyl for more power, and actually the reverse was true.