In a December report on "60 Minutes," Andy Rooney said, "There are a lot of things I'd do if I was rich... I'd fill up with high-test gas instead of the 89-octane I usually buy now."

I don't know what kind of car he drives, but if it's one that doesn't require premium, he'd be wasting his money.

And "89 octane?" If he drives, say, a Lexus or BMW (which require premium - at least 91 octane), he's likely to void his engine's warranty if something goes wrong. And if he drives something that only requires regular, well, he's pouring money down the drain.

We've always said that if your car specifies regular fuel (87 octane), don't buy premium under the mistaken belief that your engine will run better. Most cars are designed to run just fine on regular gasoline. Furthermore, many cars that recommend premium fuel also run well on regular.

What should you do - even if you are "rich?" Check your car's owner's manual to find out if your engine is designed to handle either grade. Think twice about using the more expensive gas even if your owner's manual suggests "for optimum performance use premium." We have found that the differences aren't perceivable during normal driving. However, if your car "pings" or knocks with lower grade fuel, buy premium.

Again, for all models where premium fuel is not required, buying the high-grade gas is simply a waste of money... even if you have it to burn.

What octane do you use? Post your comments below.

—Mike Quincy

Read more about fuel economy.