Gas is all refined to the same degree. The only difference is the additives the corporations put in. If any of them demonstrably make a difinitive, noticeable difference that is up to each owner's perception. One person might "feel" something in one car another guy wouldn't and things like detergent in oils also effect the engine to an unknown degree in conjunction with gas detergents so "seeing" something might be due to another factor like more or less freeway driving or a different brand of oil or even climate factors.

I've heard of more people noticing a demonstrable visual difference in internal engine parts being cleaner with high detergent oil over non-detergent oil than with any fuel additives but who knows.....