1) Yes. It is a written warranty. Examples: Direct knowledge of Amsoil buying a Toyota sludge engine owner (years ago) a replacement engine when person attempted an extended drain interval. To me, Amsoil didn't have to do this because nature of the engine. Amsoil did change their recommendations after that, so fair. Another case in 2021 a customer of mine bought MTF for their truck and shifting was very notchy and difficult, Amsoil fully refunded his money.Where is the evidence that Amsoil will stand behind their product?
Have there been any cases where the warranty was denied because of the use of Amsoil, and Amsoil covered the cost of the repair?
2) I have never in 23 years seen or been involved with a single case where a dealer tried to "deny a warranty" (really deny a claim) . It is more of a lore worry than it is made out to be.