His diagnosis and technique may be perfect for a 1990 Chevrolet Camaro, but be the worst for an Isuzu Rodeo. Also, at Express Lube, every time you walk in, they will try to sell a fuel filter, PCV valve, or an air filter. If you follow the dealer's guidelines, they will help you as much as possible. Granted, a lot of people get nervous because they were taken full advantage of by the salesman. Sales and Service are two different departments all together.
Sales is there to sell cars and have a huge income.
Service is there to help and assist with car troubles. If you do get your vehicle serviced somewhere else or do things yourself, it is very wise to save documentation to verify that the minimum required maintanence has been performed. I work for a multi-franchise import dealership. I am not bias because I have a life outside the dealership. I am telling you from personal experience.