As far as my experience goes, I have owned my 2013 ML diesel for fifteen months and it already has 20K miles on it, most suburban driving. It gets 23 miles mpg around suburbia and 26 mpg on the highway (and I drive very fast on the highway). I think diesel is the ONLY way to go for SUV driving, carrying cargo, shopping, short trips with lots of stops, etc. A nice touch is that a diesel engine heats up so much faster than gas, and after this winter that was most appreciated (as was the heated steering wheel and seats).
My only complaint is the irritaing seat belt chime which starts to ring again after a stop in the car (at a light, at the bank window, at the school). I wish the chime would ring only at the first ignition of the engine and then stay quiet. Yes I wear my seatbelt, but not every time the car is moving.
