An automobile warranty is a promise by a manufacturer or dealer that it will repair or replace defects in your car, or that your car will be of a certain quality, for a specified period of time.

Warranties are not just for new cars and are not always in writing. In some cases, even used cars purchased "as is" are covered by warranties. If you take the time to find out what warranties come with your car, what repairs those warranties cover, and how to enforce your warranties, you may save yourself a significant amount of money when your car needs repair. (To learn about automobile service contracts, also called extended warranties, see When Do You Need an Automobile Service Contract?)

Express Warranties

Express warranties are specific promises to repair your car, or statements about the quality of your car, that are written or orally communicated to you by the manufacturer or seller. An express warranty can also be created through promises in advertisements. For example, an ad claiming that "This car is made of pure steel!" is an express warranty that the automobile is made of steel. If you discover that the car is made of plastic, you can demand that the warrantor take the car back because it has breached the warranty.

All new cars come with a manufacturer's warranty that covers most repairs for a specified period of time -- usually three year to four years or 36,000 to 48,000 miles, whichever comes first. Some used cars also come with an express warranty. For example, if the car is less than a year or two old, the manufacturer's warranty may still be in effect. Or, the seller may offer a warranty that covers certain systems or repairs.

Implied Warranties

Implied warranties are not written or spoken, but automatically apply when you purchase a car (unless the car is sold "as is"). There are two types of implied warranties: the implied warranty of merchantability and the implied warranty of fitness.

Implied Warranty of Merchantability

The implied warranty of merchantability assures that an automobile will work as expected, given its age and condition. This usually means that the car is in average condition for the price paid and is fit for safe and reliable transportation. It does not guarantee a perfect car.

Implied Warranty of Fitness

The implied warranty of fitness applies when you buy an automobile with a specific purpose in mind. If you make the seller aware of your purpose for the car (for example, to climb your steep driveway) and rely on the seller's judgment to select a suitable car, the implied warranty of fitness guarantees that the car will work for that purpose.

In most states, implied warranties last forever. In a few states, however, the length of the implied warranty is the same as that of any express warranty that comes with the automobile.

"As Is" Sales

If a used car is sold "as is," the implied warranties don't apply. This means that you must pay for all repairs that aren't covered by an express warranty, even if the car breaks down on the way home from the dealership.

However, just because the seller says the sale is "as is" doesn't always mean it is. State and federal laws don't allow "as is" sales in certain situations, including when any of the following are true:

• An express written warranty exists.
• You buy a service contract from the seller within 90 days after purchasing the car.
• A state law explicitly prohibits or limits "as is" sales.
• The seller doesn't strictly comply with state law requirements for selling the car "as is."
• The seller does not provide conspicuous notice that the sale is "as is."

Enforcing Warranty Rights

Usually, you must notify the seller if you think your car does not live up to the promises in the warranty. If you keep using the car without notifying the seller of the defect, you may lose your right to enforce the warranty. Notify the seller as soon as you discover the defect, and do it again in writing if the seller ignores you the first time you complain. All warranties require that you give the seller an opportunity to fix the defect.

Always keep written records of your communications with the seller, even if it's only a note of the time and day you talked on the phone, who you talked to, and what was said. This will help protect you if you ever have to go to court or arbitration.

Not every problem or defect will qualify as a "breach of warranty." It depends on the terms of the warranty and the severity of the problem.

Also, most warranties have time limits. If you discover the problem after the warranty has expired, you will probably be out of luck. There is an exception to this rule, however: If the car was repaired during the warranty period by someone authorized by the seller, the manufacturer must extend your original warranty by the amount of time the car was in the repair shop.

If the seller refuses to honor your warranty, you may be able to cancel the sale. However, the rules for doing this are complicated. You will probably need to consult with a lawyer.

To learn about lemon laws that cover used cars, see Your Rights If Your Car Is a Lemon.