One always think to themselves, or are asked, can a dealer refuse to honor the warranty that came with your new car if someone else does the routine maintenance or repairs?

US Code - Title 15, Chapter 50, Sections 2301-2312

It's illegal for a dealer to deny your warranty coverage because you had routine maintenance or repairs performed by someone else. Routine maintenance often includes oil changes, tire rotations, belt replacement, fluid checks and flushes, new brake pads, and inspections. Maintenance schedules vary by vehicle make, model and year; the best 

What is a warranty?

A warranty is a promise, often made by a manufacturer, to stand behind its product or to fix certain defects or malfunctions over a period of time. The warranty pays for any covered repairs or part replacements during the warranty period.

Do I have to use the dealer for repairs and maintenance to keep my warranty in effect?

No. An independent mechanic, a retail chain shop, or even you yourself can do routine maintenance and repairs on your vehicle. In fact, the Magnuson-Moss Warranty Act, which is enforced by the FTC, makes it illegal for manufacturers or dealers to claim that your warranty is void or to deny coverage under your warranty simply because someone other than the dealer did the work. The manufacturer or dealer can, however, require consumers to use select repair facilities if the repair services are provided to consumers free of charge under the warranty.

That said, there may be certain situations where a repair may not be covered. For example, if you or your mechanic replaced a belt improperly and your engine is damaged as a result, your manufacturer or dealer may deny responsibility for fixing the engine under the warranty. However, according to the FTC, the manufacturer or dealer must be able to demonstrate that it was the improper belt replacement — rather than some other defect — that caused the damage to your engine. The warranty would still be in effect for other parts of your car.

Will using 'aftermarket' or recycled parts void my warranty?

No. An 'aftermarket' part is a part made by a company other than the vehicle manufacturer or the original equipment manufacturer. A 'recycled' part is a part that was made for and installed in a new vehicle by the manufacturer or the original equipment manufacturer, and later removed from the vehicle and made available for resale or reuse. Simply using an aftermarket or recycled part does not void your warranty. The Magnuson-Moss Warranty Act makes it illegal for companies to void your warranty or deny coverage under the warranty simply because you used an aftermarket or recycled part. The manufacturer or dealer can, however, require consumers to use select parts if those parts are provided to consumers free of charge under the warranty.

Still, if it turns out that the aftermarket or recycled part was itself defective or wasn't installed correctly, and it causes damage to another part that is covered under the warranty, the manufacturer or dealer has the right to deny coverage for that part and charge you for any repairs. The FTC says the manufacturer or dealer must show that the aftermarket or recycled part caused the need for repairs before denying warranty coverage.

Tips To Avoid Warranty Issues

• Read your warranty. The warranty gives a general description and specific details about your coverage. 
• Be aware of your warranty period. If problems arise that are covered under the warranty, get them checked out before the warranty expires.
• Service your car at regular intervals. This is a good idea in any case. But for the sake of keeping your warranty intact, follow the manufacturer's recommended service schedule. Details are in your owner's manual.
• Keep all service records and receipts, regardless of who performs the service. This includes oil changes, tire rotations, belt replacement, new brake pads, and inspections. Create a file to keep track of repairs; it will come in handy if you have to use your warranty. If you ever have a warranty claim and it appears that you did not maintain your vehicle, your claim could be denied.
• Complain. If you think a dealer's service advisor denied your warranty claim unfairly, ask to speak with a supervisor.