Robert is onto something when he says it is a brand thing and that Mercedes is taking great care in protecting their marque reputation. Let us face it, as clearly seen in this thread, a great number of Mercedes owners are not concerned with fuel mileage and would not buy a diesel for that reason though they might buy them as part as an overall package. A lot of Mercedes buyers in the US buy a Mercedes because it is a Mercedes, period. They want the prestige they perceive goes with the brand. I do not believe this is true in Europe, there a Benz is just another luxury car and the Europeans are not prepared to pay a high premium for Mercedes cars as americans do, the market there is now dominated by diesels (--> fuel economy). So, I agree with Robert that the decision is one of marketing and not of mpg.

Jl