Warranty Disclaimer - The Magnuson-Moss Warranty Act
Will adding aftermarket parts void your warranty? That's something previously assumed, and chances are... so have you. Some car dealerships will warn you that using non-OEM parts voids the factory warranty, or any additional warranty purchased through them. Sounds reasonable, right?
However, that is not entirely accurate. The US Government, back in 1975, passed the Magnuson-Moss Warranty Act to protect consumers from this very claim. They did this to ensure your freedom to shop for, and purchase, aftermarket parts and upgrades is protected from both unscrupulous dealerships and manufacturers.
Magnuson-Moss requires that dealerships and/or auto manufacturers prove that a failure is directly caused by the modification to the vehicle with aftermarket non-OE parts. Furthermore, even if they do find that the aftermarket modification/part caused the failure, it only applies to that claim. Which does not necessarily mean the warranty is now void. In other words if you install an aftermarket air filter and it ruins the Mass Airflow Sensor, it's not covered. However, the remainder of your warranty... suspension, transmission, etc. is not affected.
In addition to Magnuson-Moss, the Federal Trade Commission (FTC) issued an opinion that confirms that it is illegal to void warranties or deny coverage for use of aftermarket parts. They also clarify in the alert that the protection extends to routine maintenance. In other words... the vehicle warranty is not tied to dealer services (like oil changes). You can read more, here.
If for some reason, a dealer or manufacturer denies your warranty claim you should file a complaint with the FTC as soon as possible.