Originally Posted By: StevieC
Why wouldn't the Magnuson Moss act not step in? (I'm asking, not arguing)
As for being without your vehicle you would be anyway with any warranty claim. Sure it might be longer while the engine is inspected but it's not like we are talking a year or anything. They will know quickly what caused it and where the fault lies. As least my dad and I can so I would assume a grease monkey at the dealer could too.
In theory, yes, the Magnuson-Moss Warranty Act should step in. However, it's how the Act is worded that provides uncertainty for the vehicle owner.
To keep it simple (and within the framework of my understanding), the MMWA states that it is the responsibility of the Manufacturer to prove that the use of an aftermarket part (in this case, a non-API certified oil) caused the damages. If they cannot prove that, the warranty must be upheld.
Before we proceed, however, understand that in the U.S., "breach of contract" is a civil matter and the rule of thumb governing civil cases is "by preponderance of evidence" meaning that a majority of the evidence must point in a certain direction. In a fictitious case, if 51% of the evidence says a defendant is not guilty, the defendant would be considered "not guilty" even though 49% of the evidence showed that the defendant was guilty. This will be important as we go forward.
If you make a powertrain warranty claim, the Manufacturer is going to look for ways to get out from their warranty burden. It's all about money. If you used a non-API certified oil, they will look for any reason that the use of this oil caused the damages. At this point, it's a calculated gamble. If they feel like they can prove "by preponderance of evidence" that the oil is what caused the damage, they will deny the warranty claim and put the onus on the vehicle owner to fight the denial. At this point, it puts the vehicle owner in a difficult position of weighing the cost of fighting this though the courts and paying those associated fees if they are ruled against versus simply paying the cost of repairs. This doesn't include the time it would take to get through the courts, which would be entirely too long for many who rely on their vehicle for daily operation.
Where the MMWA can help the vehicle owner is if the failure is one that could be considered "common", where the Manufacturer knows that they cannot pin the failure on the non-API certified oil because there are other cases of failure of the same part in which API certified oil was used. An example would be the Theta II engine recalls faced by Hyundai recently. If you experienced a failure that fell under the recall and you used Amsoil (in this instance), you would likely not be denied coverage due to the sheer numbers of failures wherein oil with the proper certification was used. If you were denied coverage, it would be easier for the vehicle owner to fight the denial due to the "preponderance of evidence" that motor oil is not the root cause for the Theta II issues which were found to be caused by issues in the manufacturing process.
TL;DR- Yes, the MMWA is their to protect the consumer. The way it is worded, however, does leave a window of opportunity for Manufacturers to take a calculated risk and deny coverage. If you feel that you have been improperly denied coverage, you can file a complain with the State Attorney General, a local Consumer Protection Office, or the Federal Trade Commission.
EDIT: here are some links for reading on the issue, if you want further information. Also, I'm not a lawyer so this is simply my understanding of the law.
FTC
Cornell Law
FTC filing regarding API and dexos certification