This was posted by epolk-most excellent post:
"Respectfully, that's dead wrong! I do happen to be a lawyer (at least I was before the USMC "invited" me back... ) , let me explain. In the US, new car warranties are governed by the Moss-Magunson Warranty Act (MMWA). Although the wty may have the trappings of a contract, and has some characteristics of a contract, anything in it that purports to give you lesser or fewer rights than the MMWA requires is simply not enforceable.
More importantly, Ray is right. If the mfr does say "denied" and you take them to court, THE MANUFACTURER must prove that the failure was a result of something you (or some third party) did, as opposed to being a result of a manufacturing defect. If they can't prove this, they lose, period. And they get to pay for your attorney's and fees, in most cases. They may bluff at you some, but if and when you show up with a lawyer who knows what he or she is doing, they'll settle up unless they've got iron clad proof that you're at fault.
And pertinent to this thread, merely not changing oil when the mfr recommends is NOT proof of anything. The easiest wty case for an owner to win is when the mfr or dealer admits up front that they're denying a claim because you didn't follow the schedule. No such "penalty" is allowed. They can only deny the claim if they can prove a causal LINK to the claimed failure. And even if they do, the wty is still in full force as to any other unrelated defects.
EDIT: The MMWA does NOT generally apply to those after-marked extended wtys, so with those, you do need to do what's set out in the agreement. But don't let a mfr buffalo you about the protection in your standard wty."
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=1;t=015645;p=1