Quote Originally Posted by SpecV_Scott
The one thing this article doesn't mention is that while there isn't a difference in MPG between 87 and 93 octane gas in general, that isn't necessarily the case in practice, especially in high performance cars. Think about what most ECUs do when they detect knock...they retard the timing. Sure you can get away with driving around with your timing retarded...but you will definitely not be running as efficiently as you would with your timing at ideal levels.

So it may cost 30c/gal more, but you will probably get better mpg if you drive a highly tuned and/or performance car. Otherwise, use 87.
My car from the factory came with a sticker that says "Premium Recommended" and I can tell a difference between running regular vs. running regular. Let me tell you on regular, the fuel needle really moves. If I get 300 miles with regular I'm doing really well. And that's acutally driving normally. On premium, I get way better. I get close to 30 mpg on the highway with it. I filled up with regular and not only is it slower, but I'm probably getting about 22-24 mpg right now. Sux for me.