Johnny Rad

The M278 debuted in the '11 CL550, if I recall correctly. It then showed up in the CLS, E, GL, ML and S.

Is it a car motor adapted to truck usage?

Or, is it a truck motor adapted to car usage?

Does it even matter these days? If it doesn't today, why did it used to seemingly matter?

Aside from psi and maybe an ECU difference, what changes has Merc made between car and truck M278's - strengthened block, different Johnson rod (Seinfeld), etc???

pjw1967

Off topic, but historically related. We all know the small block. It's big brother was the 348, which was a truck engine. It first appeared in Chevys in 1958, some with tripowers. It later became the 409 from the song of the same name. But it didn't breathe very well when used as a race engine, which led to the introduction of the big block.

Munich77

I think it is a passenger car engine - I would not consider the GL and ML trucks in the truest sense. They are not that much heavier than the S-class. Apparently there is not much difference in the engine in the passenger car.

homeyclaus

The difference between truck and car engines is primarily cooling, since commercial engines usually run higher loads. Private light duty trucks don't do that, but they do tow, so those cooling systems need to handle that.

Look at the v6 diesel engines in the sprinter vs the e350, same engine, big difference in radiator size and cooling system capacity, and likely shorter maintenance intervals.