Switched to synthetic oil in my 6.7 Cummins at 180k miles

After running conventional for so long I saw the oil analysis come back way cleaner at 5k miles versus the old stuff at 3k. Anyone else notice a big difference in engine noise or oil life after making the switch?

2 comments

2 Comments

the_oliver16d ago

Wait, you're saying switching actually helped with noise? I always thought synthetic was overrated for older diesels.

susan8115d ago

Did you ever check your injector timing after the switch? I've seen a bunch of old diesels quiet down just because the synthetic oil let the injection pump work more freely, which changes the spray pattern slightly. That knocking noise people hate on older diesels is often a timing or injector issue, not just the pistons slapping around. Most guys blame the oil weight or viscosity but overlook how the pump's internals are lubricated differently. It's a sneaky thing that makes synth look like a magic fix when really the pump was just struggling before. Have you noticed any difference in cold starts since you switched?