Re: Can synthetic oil be put in at 5K miles? (judah)
I read that Mobil 1 is no longer "fully" synthetic unless you use 0w-40. Their tri-synthetic formula has a higher pour point than their older 5w-30 and up oils. Their 5w-30 used to meet the specs for use in Mecedes diesels, but the tri-synthetics do not. Only the 0w-40 meets the specs. You might consider Amsoil which has not changed.