Switching to synthetic oil in an old Detroit - worth it or asking for trouble?

I've got an old 8V92 in a truck I've been working on, from like a 1985 rig, and it's got maybe 400k miles on it. Always ran conventional 40 weight in it, no complaints, but I've been reading about synthetic blends cutting down on smoke and maybe helping cold starts. A buddy of mine says synthetics will clean out all the old sludge and cause leaks where there weren't any before, make a mess. But another guy I work with swears he switched his old 6-71 over to full synthetic at 300k and it ran smoother and lasted another 200k without issues. I'm torn, I mean the truck runs fine now but if it could be better why not try it? Has anyone here actually made the swap on a high-mileage older Detroit and had it go either way?

2 comments

2 Comments

hannahh5314d ago

Nah, go for it. I switched my old Cummins over and it cleaned things up without any leaks.

leobrown14d ago

Ngl I gotta push back a little on "cleaned things up." A Cummins swap ain't really gonna clean anything up unless you're talking about the oil system specifically. The old mechanical pumps just don't make a mess like the newer electronic ones do. If you had leaks before, it's probably because of bad seals or loose fittings, not the motor itself.