I have a co-worker whose mechanic father told her to put in premium gas once in awhile, because it will clean out deposits that are left behind from using the regular fuel the car was designed to use.
I don’t think this sounds correct… Is it?
All gas now have detergents. Premium gas is no better a cleaner than regular gas and needs to be used only in those engines that demand the higher octane. Otherwise, it’s a waste of money.
I second what barbitu8 said. Premium gas is only for cars that need it to prevent engine knock. Putting in a higher octane gas than your car’s engine needs is a total waste of money.
Tom and Ray have been saying for years, “If your car was designed to run on 89 octane, put 89 octane in it!”
Who are we to argue with them?
An even more appropriate link.
I’ve been using Premium gas in my 1992 Honda Accord for 9 years (since I bought it). Will changing back to Regular hurt it now?
An engine with a lot of miles on it sometimes has compression problems, in which case higher-grade gasoline probably will improve performance. There’s no reason not to try the regular, JJ, but you may notice an increase in engine knocking now that your Accord is a senior citizen.
But whatever you do, don’t try to figure out how much money you wasted buying high-octane gas when the car was new and it didn’t really need it. 
If your car knocks and pings when you switch back to regular then you should continue with premium until you fix the problem. Your car shouldn’t knock or ping on regular gas, and switching back won’t hurt it. But premium may be masking problems with compression or timing.
A '92 Honda is a senior citizen? Then what are all those early '80s Hondas I see all over the place?
As others have stated, there is no difference in the detergent qualities among various grades of gas. However, Chevron does use a patented additive, Techron, which apparently is pretty effective at cleaning deposits. You would probably need to use Chevron pretty regularly to see the benefit since they probably don’t put much of the stuff in their gas. Or you can do what I did and run down to your auto parts store and buy the Techron additive to add to your gas. It’s not anything that needs to be used on regular basis, but rather is a once in a blue moon type of thing. If you’re planning on using an additive, I’d use that one.
I’ll bet that Stupendous man’s co-worker’s dad was referring not to premium gas in general, but rather gasoline that has been blended with ethanol to enhance its octane number. I’m not sure how easy to find ethanol-gasoline mixtures are, but this site claims that “[e]thanol-blended fuels account for 12% of all automotive fuels sold in the U.S”
Anyway, this site claims that “[t]he ethanol in E-10 Unleaded actually keeps fuel injectors cleaner-helping improve engine performance” and “[t]he ‘cleansing’ nature of E-10 Unleaded with Ethanol can actually keep your fuel system cleaner—and lead to improved performance.” No proof, of course, but it seems plausible to me that the ethanol in gasoline would loosen deposits left in fuel lines and injectors. Does that lead to increased performance? Dunno. Anyone else care to speculate?