T
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Switched to synthetic oil in my old Cummins and I'm eating crow now

Always ran conventional Rotella in my 12-valve because that's what the old guys said to do. After 320k miles the overhead started clattering cold, so I finally caved and went full synthetic 5w-40. Quieted down in 2 days and the oil analysis came back cleaner than any winter batch I've had. Anyone else stubborn about this or am I late to the party?
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3 Comments
the_pat
the_pat16d ago
320k miles on conventional and it was still running fine... I don't buy the synthetic miracle cure thing personally. Had a friend switch his 7.3 over at 250k and all it did was start leaking past some old seals that the thicker oil was holding together. Ended up costing him more in gaskets than the oil was worth.
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jennifer965
320k miles on conventional is pretty solid proof that dino oil gets the job done. All these stories about synthetic fixing everything just seem like wishful thinking to me. If it ain't broke why mess with it? Your buddy's leak situation is exactly what I've heard from a few other guys too.
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terryf62
terryf6216d agoMost Upvoted
quieted down in 2 days" is interesting lol, buddy of mine had the same thing with his old Powerstroke, swore by dino oil for years and the synthetic stopped his cold start rattle in a week.
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