I've had a 601.921 engine head gasket go bad too, but that's rare (far less than even 5% by my count) and the cost of replacement (including a new chain and tensioner while he was in there) was WELL under $1000. I'd sure wait for it to happen since it seems to me that fewer than 1 in 20 are going to fsil. More than half of the 60x engines I've owned (and I've owned 7 of them) have a minor oil ooze at the right front corner of the engine where there's and oil passage that sticks out past the far right front head bold (seems like bad design to me) and a lot of other OM60x owners confirm this as well but none were bad enough to require a new gasket. My failed head gasket failed between the #1 cylinder and the chain vault and I've seen/heard of several other 601 gaskets (including 601.91x 2 liter versions) fail exactly there.

Marshall