My uncle swore by a 10W-30 oil for a 6.7 Powerstroke in Texas heat.

Tried it for a summer and the oil pressure dropped way low on long hauls. Anyone run into this with modern diesels?

2 comments

2 Comments

Gotta disagree here. Modern diesels run crazy tight tolerances and need the exact oil weight. That 10W-30 is just too thin when it gets hot under a real load. Saw the same pressure drop on a buddy's truck. Switched to a 5W-40 full synthetic and it fixed it. The engineers pick those specs for a reason.

owens.nancy1mo ago

Yeah, the tight tolerances thing is real. I ran a slightly thinner oil in an old gas engine once and the pressure just vanished when it got hot. Switched back to spec and it was fine.