The Magnuson-Moss Warranty Act: maintenance and your car warranty

The short answer

What the Magnuson-Moss Warranty Act says

The Magnuson-Moss Warranty Act of 1975 is the federal law for written warranties on consumer products, cars included. The part that matters for maintenance is Section 102(c), at 15 U.S.C. § 2302(c). In plain words, it says:

• A warrantor (the company that gives the warranty) can’t make the warranty depend on your using a part or service identified by brand, trade, or company name.
• Exception 1: if the warranty provides that part or service free of charge, the company can require its own.
• Exception 2: the FTC can waive the rule if the company proves the product works properly only with that brand, and the FTC finds the waiver is in the public interest.

The FTC enforces the law. In its business guide, it calls these “tie-in sales” provisions and says that, generally, they aren’t allowed. In 2022 it took action against Harley-Davidson and Westinghouse (an outdoor power equipment brand) for warranty terms that suggested coverage would be void if customers used independent shops or third-party parts.

Dealer vs independent mechanic

You can choose. The FTC says manufacturers and dealers can’t deny coverage simply because someone other than the dealer did work on the car. That covers an independent shop, a chain, and your own garage.

What still matters is that the work is done right and on time. If a repair or maintenance job done elsewhere actually causes a failure, the maker can refuse to pay for that damage. The FTC’s business guide says a warrantor may exclude damage caused by parts or service it didn’t provide. The burden is on the dealer or maker to show that the outside work caused the problem.

A practical point: warranty repairs and recalls themselves are done at a dealer, at no charge. Routine maintenance can be done anywhere.

Does doing your own oil change void the warranty?

No, not by itself. Do these three things, and a DIY oil change is as good as a shop’s for warranty purposes:

1. Use what the manual specifies: the oil grade (such as 0W-20) and any required certification, and the right filter.
2. Change it on time by miles or months, whichever your manual says comes first.
3. Keep proof: dated receipts for the oil and filter, and a log entry with the date and odometer reading.

The same goes for filters, spark plugs, and other routine work. For the intervals, see how often to change oil and your car’s maintenance schedule.

Aftermarket and recycled parts

Using an aftermarket or recycled part doesn’t void the whole warranty. The FTC says a maker may not deny coverage unless it can show that the aftermarket equipment caused the need for repairs, and the rest of the warranty stays in effect. Example: a non-brand oil filter doesn’t void coverage of your infotainment screen. If that filter failed and damaged the engine, the engine repair is where the question comes up.

Performance changes are a different matter. Engine tuning, lift kits, and similar modifications can lead a maker to deny claims for the parts they affect, if it can show the link.

What can void a car warranty

Read the “What is not covered” section of your warranty booklet. Common exclusions there include:

• Damage caused by skipped or late maintenance, such as an engine failure after oil changes were missed
• Damage caused by a part or repair from someone else, if the maker can show the link
• Misuse: racing, overloading, or towing beyond the limits in the manual
• Damage from accidents, floods, or fire (that is an insurance matter)
• Wear items, such as brake pads, wipers, and tires (tires often have their own warranty from the tire maker)

The exact list differs by carmaker and model year, so the booklet decides. Timing belts are usually treated as maintenance: Consumer Reports notes they usually aren’t covered under warranty.

Complimentary maintenance plans

Some carmakers include free scheduled maintenance for the first years or miles. Because that service is free, the law lets the maker require its own dealers to do it. You can still pay an independent shop for other work. If you skip the free visits, keep proof that the maintenance was done somewhere else on schedule.

Keep proof of maintenance

The FTC advises keeping all service records and receipts, whoever does the work. A good record shows:

• The date and the odometer reading
• What was done, with parts and fluids (brand, grade, part number)
• Who did it: the shop’s name and address, or “owner”
• The receipt for parts or the shop invoice

How to keep them so you can find them years later: car maintenance records. To log each service as you go, use our free car maintenance log.

If a warranty claim is denied

1. Ask for the reason in writing, including what the dealer says caused the failure.
2. Show your records: receipts and log entries for the maintenance in question.
3. Go up the chain. The FTC suggests talking to a supervisor at the dealer, then the manufacturer, or another dealer.
4. Complain to your state attorney general, a local consumer protection office, or the FTC (ReportFraud.ftc.gov).

State “lemon laws” cover new cars with repeated defects; your state attorney general’s office explains the rules where you live. This page is general information, not legal advice. For a large claim, consider talking to a consumer lawyer.

FAQ

What is the Magnuson-Moss Warranty Act?

A 1975 federal law on written warranties for consumer products. For cars, its best-known rule (15 U.S.C. § 2302(c)) bars a maker from requiring brand-name parts or service to keep the warranty, unless it gives them to you free.

Does doing your own oil change void your warranty?

No. Use the oil and filter your owner’s manual specifies, change them on schedule, and keep dated receipts and a log with the odometer reading.

Can a dealer deny warranty coverage for using an independent shop?

Not simply for that, according to the FTC. The dealer or maker has to show that the outside work or part caused the problem before it can deny coverage for that repair.

Do aftermarket parts void a car warranty?

No. A maker can deny coverage only for damage it can show the aftermarket part caused. The rest of the warranty stays in effect.

What maintenance records should I keep for my warranty?

Dated receipts and invoices for every service, with the odometer reading, the parts and fluids used, and who did the work. Keep them for as long as you own the car.

Sources

• 15 U.S.C. § 2302(c), Prohibition on conditions for written or implied warranty (Magnuson-Moss Warranty Act, Section 102(c); checked November 12, 2026): law.cornell.edu
• Federal Trade Commission, FTC offers tips on making the most of your auto warranty (January 14, 2011): ftc.gov
• Federal Trade Commission, Businessperson’s guide to federal warranty law (tie-in sales provisions): ftc.gov
• Federal Trade Commission, Auto warranties and auto service contracts: consumer.ftc.gov
• Federal Trade Commission, FTC takes action against Harley-Davidson and Westinghouse for illegally restricting customers’ right to repair (June 2022): ftc.gov
• Consumer Reports, The cars and SUVs with the highest repair costs for common fixes (timing belts usually not covered under warranty): consumerreports.org