These aren't warranties so much as insurance policies complete with deductibles and other insurance-like rules.

They're big profit makers for dealerships, so don't be surprised if your salesman pushes 100,000-mile "bumper-to-bumper" protection very hard.

But extended warranties are rarely worth the extra cost.

That's especially true if your new car or truck already comes with one of the great 60,000- or 100,000-mile powertrain warranties that many makes are offering on 2008 models.

While they don't cover some major components such as air conditioners, cooling systems and electronics, they do cover engines and transmissions -- the most costly parts to fix.

Click here to learn more about the 5 best warranties for 2008. They're the best we've ever seen.