Forget MPG ... Best Long Term Option 50i or 35d

[JCL]

Originally Posted by docpowell

Diesel longevity has been proven time and time again. And in most cases a diesel doesn't even get truly, "broken in," until the 60K-80K mile mark. And though the US spec diesel is fairly new, and the 09 model had several bugs in it, overall the M57 is a proven engine as well as the seemingly bullet-proof tranny, makes the diesel, in my opinion, the obvious choice.

It is really difficult to compare large displacement (11-15 litre) medium duty diesels to 3 litre automotive diesels. Wet cylinder liners, heavy cast blocks, and so on, vs aluminum blocks, just for a start. Fuel system complexity is significantly different, at least until medium duty diesels have to meet the same emissions standards. The old automotive diesels that ran forever (Mercedes, Peugeot, etc) were low speed, heavy, low tech diesels. They have almost nothing in common with modern automotive diesels. A far better comparision to an automotive diesel would be the Oldsmobile V8, with the diesel that was made out of a gasoline engine. That didn't work out so well. Or consider the Smart diesel. I don't think that will just be getting broken in at 80,000 miles.

I think a 3 litre BMW diesel will last just fine, but it will wear out a little bit sooner than the similar 3 litre gasoline version due to the higher peak cylinder pressures, and a little bit later due to the lower revs. Probably a wash overall. Both the diesel and gasoline versions will last longer than the rest of the vehicle, however.