P.T. Barnum said "There's a sucker born every minute," before the dawn of mass-produced automobiles, but peddlers of bogus mileage-enhancers and proponents of unnecessary auto maintenance procedures are carrying on Barnum's tradition. Everything from magnets to vortex generators to water injectors and useless "ectoplasm traps" are hawked in the marketplace, and unnecessary tune-up processes can further bleed consumers' wallets. The best defense is to read your owner's manual and bone up on your car's needs, but in the meantime, here's a 5-point list of dubious or unneeded engine-enhancing procedures.

Engine Flushes ($100-$200)

An engine flush uses a machine and chemicals to rid your engine's innards of sludge, but it's not a normal maintenance checkpoint unless you've neglected your engine. We checked in with Tom Torbjornsen, maintenance editor at AOL Autos for his perspective.

"Change your oil according to manufacturer's recommendations and you won't need an engine flush," Torbjornsen said.

An examination into your oil-filler lid will reveal deposits and gunk.

"Sometimes, if you've got an engine with high mileage and deposits, a flush will break loose sludge that can get into the engine," he said. "It's really not necessary today if you've otherwise taken good care of your car."

Fuel-Injection Cleaning ($125-$200)

"If your Check Engine light isn't on and your car's running fine," says Popular Mechanics's Mike Allen, whose team of testers have debunked dozens of phony gadgets, "Skip this."

Torbjornsen agrees.

"An upper engine carbon cleaning is a good thing to have every 35,000 miles because of varnish deposits," Torbjornsen said. "When fuel injectors get dirty and deposits build up, you get poor fuel economy. But not every year. Once a year is overkill."

Oil Additives ($5 AND UP)

There are numerous oil additives on the market ranging from products designed to reduce friction and bolster fuel economy to those whose manufacturers claim their product will allow you to run your engine dry of oil without damaging bearings. Steer clear of all.

"Oil additives are designed to fortify and bolster the engine," Torbjornsen said. "But if you're following normal maintenance producers, you don't need it. In the testimonials you'll find on websites selling this stuff, people say they can drive without oil because of some magic elixir. But a real-world tester always fails."

Gas Savers ($10-$400)

Some of the pseudo-scientific gas savers on the market just plain don't work and may actually hurt engine performance, says Torbjornsen. The E.P.A. has tested over 100, from pills you pop into your tank to "cow magnets," and none have proven effective.

"Some of these products claim to 'polarize the molecules in the vortex'," he said. "It's all garbage."

Long-Life Antifreeze ($4-$8 Per Quart)

There isn't any evidence that "long life" antifreeze is any better for your radiator than standard antifreeze, and you shouldn't assume that because you've bought and used it, you can ignore maintaining your radiator, says Torbjornsen.

"I recommend a 2-year, 24,000 mile flush regardless of what kind of antifreeze is in your radiator," he said.

"Especially if you live in a wintery climate."

And don't mix coolants, either, says Allen.

"That's asking for trouble, especially if your car's engineered for a specific type of anti-freeze."