M servicing is a complete con imo, get the dealer to give you a copy of the check list, very little is done ,its just a check that says , it aint broke yet! Very little stripping , cleaning and greasing as in old fashioned preventive maintenance. You get the valve clearances checked, but only adjusted if not within tolerances, and we have all heard the dealer stories" oh we just listen to them and if not noisy we leave them alone. Some dealers charge extra for coolant and brake fluid changes on top of inspection 1 and 2 charges. I have recently done my extra to service history interim oil change, when i removed the engine undrtray. I found all the bolts and screws semi siezed because the last bmw tech couldnt be arsed to put a bit of copperslip on them when he reassembled lasr service, that is basic good mechanicking so you know they will undo next time, imo you need to get down and dirty under your car to check the dealers work, correct their lack of attention to detail. Do the little thimgs that they arent paid to or cant be arsed to do and your car will be way better cared for than just presuming they are going to do a good job because they are main dealers!!