Even if your car is from the same brand as the dealership, they may not be equipped to service it. At what point does that become reasonable? Just how old is too old?
For example, Mazda rotaries are infamous for being unservicable at Mazda dealerships, even when the RX-8 was barely a decade old.
from working at the only mclaren f1 service center in na as a car washer for I learned that only bmw dealers are allowed to touch the engine so one of the local bmw dealers is wualified to work on it