Swapped from synthetic to conventional oil on an old Cat 3406 and it stopped leaking
My mechanic buddy swore the synthetic was too thin for the high miles, so I tried conventional and after 2 weeks the drip under the pan went away - has anyone else seen that with older engines?
Wait, the synthetic was actually dripping out that bad? That stuff is usually thicker at operating temp, not thinner, so that's weird to hear.
I had a 3406B that would weep a little at the rear main on Rotella 15W-40, but when I tried a high-mileage synthetic blend it actually slowed the leak down after a month or two. Maybe your engine just has a specific wear pattern that hates the detergents in synthetic. That's a new one on me.