Never buy a higher grade of gasoline than your engine needs.

If you think you're doing your engine a favor, or teasing it into making more power by filling up with premium fuel, you might as well be lighting your spark plugs with $20 bills.

Modern automotive engines are computer-controlled to operate within a tight range of operating parameters, and that includes how much octane is in the gasoline you use.

Almost all engines run properly on the 87-grade octane regular gasoline that is the least expensive at the pumps, and the engine won't generate any more power if you fill up with premium.

Just follow what your owner's manual says.

If it -- or your gas cap or gas gauge -- has a label saying "premium recommended," ignore it. You'll never notice the small amount of power the engine will produce with higher-octane premium gasoline.

No engine needs midgrade fuel, so don't waste your money on that, either.

The only reason to put the high-octane hose in your car is if your owner's manual says "premium required."

Those usually are luxury and performance cars with high-compression engines, plus a few Volkswagen and Mini models that you wouldn't expect to need premium fuel, but they do.

With premium costing about 30 cents more than regular, you can blow $20 or $25 a month, or several hundred dollars a year, using the wrong fuel.

Here are some more ideas on how to save on gas.