Gilly:

I hear what you say, but it sounds more like a service writer (salesman) talking to me who is looking to sell me unnecessary services. This is the first time I have ever heard of "any" manufacturer requiring spark plug replacement based upon a calendar time requirement. I can understand an engine hours of operation requirement, but this sounds like a real money making scheme for Mercedes techs. If the only purpose is because of the spark plug seizing in the hole over a certain period of time, why not just use antiseize compound? If antiseize does not work, why not just remove the plug, clean and replace the antiseize, and reinstall?

Mercedes is telling us the transmission fluid is a lifetime fill and engine oil changes only need to be done at 10,000 - 12,000 mile intervals but sparkplugs have to be replaced every four(4) years. What's wrong with this picture?

When Mercedes adopted the FSS system, went to 100,000 mile plugs and made other changes, I thought the primary purpose was to reduce the amount of periodic servicing required for a Mercedes vehicle to make them more competitive with other vehicles that did not require the extent of servicing of a Mercedes.

I am becoming convinced that the only purpose of the 4 year/50,000 mile free maintenance that Mercedes offers is to keep the typical first buyer (who usually only keep their cars during the warranty period) from seeing the true cost of Mercedes ownership. They only care about the original owner and no longer care about lifetime durability. Keep people trading ever few years (its cheaper than owing long-term) and pump up the new car sales volume. The Chrysler philosophy is bleeding all over them! Hopefully, some day the Mercedes techs will reduce their hourly shop charges from $100/hr. to $75/hr. like the Chrysler techs charge.