 Dealerships pretty much have a lot of control over what they can warranty and not warranty. The manufacturer gives them a lot of leeway. Where it gets dicey is if you get into an engine replacement or something along those lines. They may have to get some zone approval or things like that. But remember, the larger the dealer, the more pull even with their local zone rep they have and the ability for them to overwrite things and get things handled, especially when they've done, quote-unquote, the maintenance on the car.