funnyman06 wrote:
When I had my engine rebuilt recently the mechanic who rebuilt it told me to not use Synthetic oil in the jeep and to stick with plain ol 15-40 dino diesel oil, and to also keep the oil change intervals to around 3-4K. His reasoning had to do with the ability of synthetic oils to wick heat away vs conventional, and how that relates to us having piston oil squirters. I just did an oil change on it and used the M1 301 filter and 7 quarts of Mobil Delvac 15/40. But typically I would use Rotella T6 and a Wix or Purlator Filter.
I think your mechanic should go to requalify regarding oil topic. It make absolutely no sense to say what he says, since it is proven that synthetic oil resist better shear and it is more fluid (usually) than conventional oil. A more fluid oil will always cool better and go easier through tiny passageways. Oils with higher shear point would also lube better than oils with lower in high operating temperatures like diesels usually have in combustion chamber. Better would be to say that the risk of synthetic oil to shear is way less than at conventionals. Your mechanic has absolutely zero scientific proof to support what he sad. That's not to say you'll ruin the engine running a conventional 15w40, but I one would not even think going with synthetic. Even big 18 wheelers can use synthetic better than conventional, the problem is the costs, especially that those engines barely go close to 2k rpm and they operate 99.9% on engine recommended temperatures when flow rate does not vary so much between conventional and synthetic.