Blue Oval Certification, it gives the dealer a better relationship with Ford Motor Co, the dealer will get better pricing on new cars, wholesale costs on parts and various programs in the service dept. The dealers must maintain a standard set by Ford Motor and the dealers are scored against each other in their region. The service managers and service writers do get a extra $$$$ from the program, but they will also get booted by the dealer if their rating goes too low.
If you are satisified with their service, forget the oil change, the best play for you is to make sure the service manager knows you gave them a perfect score, this way if any future problems come up, you most likely will be taken care of and try to use the same dealer. Just to give you an example, they have something called a "Good Will" account, if your outside of your warranty period and your transmission goes, they could use Good Will money to fix your car free of charge to you.