VEHICLE WARRANTIES & THE USE OF AFTERMARKET PARTS: The affect of performance and aftermarket parts on automobile manufacturer's consumer warranties is a subject of great misunderstanding. The simplest and clearest explanation, popularly derived from the Magnuson-Moss Warranty Act (US Federal Trade Commission 1975), is as follows: a manufacturer cannot deny a customer�s warranty claim because his/her vehicle contains aftermarket parts unless the manufacturer can prove that the aftermarket part directly caused the failure that initiated the warranty claim.

On July 4, 1975 the Magnuson-Moss Act, enacted by Congress six months earlier, went into effect. It is part of the official United States Code and can be found at 15 U.S.C. 2301 et. seq. Section 2302(c) specifically addresses the issue that most people reading this page are concerned with. In pertinent part it states:

"No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer's using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name. . . . 15 U.S.C. 2302(c)."

The aforementioned Act text is found in the section addressing "Tie-In" Sales Provisions. Tie-in sales provisions force the purchasers of warranted products to buy items or service from a particular company for use with the warranted product in order to be eligible to receive a remedy under the warranty. This practice is prohibited.

The following are examples of prohibited tie-in sales provisions.

- In order to keep your new Acme vehicle warranty in effect, you must purchase and use genuine Acme brand oil filters and other maintenance parts.
- Failure to have scheduled maintenance performed, at your expense, by an authorized Acme dealership repair center voids this warranty.

Additionally, Congress supplemented the Act in 1977 when it interpreted the Magnuson-Moss act. This interpretation appears at 16 C.F.R. 700.10 section 102(c) and states, in pertinent part:

"No warrantor may condition the continued validity of a warranty on the use of only authorized repair service and/or authorized replacement parts for non-warranty service and maintenance. For example, provisions such as, 'This warranty is void if service is performed by anyone other than an authorized "ABC" dealer and all replacement parts must be genuine "ABC" parts,' and the like, are prohibited where the service or parts are not covered by the warranty. These provisions violate the Act in two ways. First, they violate the section 102 (c) ban against tying arrangements. Second, such provisions are deceptive under section 110 of the Act, because a warrantor cannot, as a matter of law, avoid liability under a written warranty where a defect is unrelated to the use by a consumer of "unauthorized" articles or service. This does not preclude a warrantor from expressly excluding liability for defects or damage caused by such "unauthorized" articles or service; nor does it preclude the warrantor from denying liability where the warrantor can demonstrate that the defect or damage was so caused."

The aforementioned text is generally understood to mean that, although a manufacturer cannot attach its warranty to a tie-in sales provision, it is not required to warrant the use of replacement parts, repairs, or maintenance inappropriate for its products. The following is an example of a permissible manufacturer warranty provision that addresses this issue.

- While necessary maintenance or repairs on your Acme can be performed by any qualified automobile repair shop, we recommend that you use only authorized Acme dealers as they are best qualified to work on Acme products. Improper or incorrectly performed maintenance or repair work can void your car's warranty.

So what does this all mean for the owners of modified cars? It means that, (for example) according to the law, if you install a tubular sway bar kit on your car and the turbo blows, the manufacturer cannot deny you warranty coverage on the turbo simply because your car contains aftermarket parts. (There's no way that sway bar kit caused your turbo to blow). But, if you increase your car's engine torque by (for example) 30% and subsequently burn out the clutch (which was not designed for that kind of load), the manufacturer probably can deny your warranty claim on the clutch. And that's only fair.

While the examples above may seem to make the situation clear, there are many gray areas that defy easy interpretation. What (for example) if you've lowered your car and later the ball joints give out? Did the lowering cause this failure? Or would it have happened anyway, even if you had not lowered the car?

Additionally, what the law says and what your local dealerships practice may be two different things. Some dealerships won�t touch a car that's been modded, period. Others will gladly do modifications for you right at the dealership.