If you want to be safe, send them an email and get something in writing. My comments don't have any legal bearing on your warranty contract. I just know what I'd do.... and I'm also capable of making technical arguments to ensure I'm covered based on 5k intervals with synthetics. (In other words, I'd make it more of a nightmare for them to try denying my claim than its worth. But that how insurance companies make money.... they deny claims and see who bites)