[Steiglitz]

True, one could use just conventional and get a zillion miles out of their engine with no problems. The conventional oils of today are great and lightyears better then conventional just 10 years ago. The gap in protection between conventional and synthetic has greatly narrowed. I use synthetic for it's better flow properties, and better protection at start up, but once the oil is up to optimum operational temperature, the synthetic probably does not protect any better then conventional, except maybe if the engine is running in an over-heated state. As to better MPG, using synthetic will increase it in a very, very small amount. If the dealer is offering free oil changes, then it would be wasteful to buy your own and leave it with the tech....the difference in MPG is way, way too slight, and therefore this is a waste of your hard earned money.