He's probably talking about the Mercedes diesel used in the dodge sprinter. It's a fine engine as long as you don't treat it like an old low pressure injection diesel (which most guys who buy them probably do).

For years guys with diesel engines would add all kinds of oils and lubricants to their diesel fuel because in the early 90's, when they went to low sulfur fuel, they didn't get the formula right and it would kill the fuel pumps.

Guys think the same thing will happen now (since they lowered the sulfur content again last year), so they add oil, power steering fluid, and all kinds of other stuff to their fuel. This kills the injectors, the fuel pump, the cats, the exhaust filters, and just about every other component except the shortblock and the turbo.

Mercedes makes solid diesel engines, but a lot of guys don't understand the differences between the new clean diesels and older diesels. Very different in quite a few ways, both in the way they operate and the way they are maintained.

(I've worked as a diesel mechanic as well, so I've played with most of them. Though, usually the stuff I work on is bigger.)