this is what a guy posted over in this one site I goto. I think he is full of BULL> but what do I know. let you all let me know .
quote:so what do you all think. right? some what right? or dont know what he is talking about?
Don't know if anyone has said this yet, but: Synthetic oils are fine for ALL vehicles, but if yuo are running a high mileage engine and want to switch to synthetic, pull the pan, and clean out the sludge first. Synthetic oils have about 5x the amount of detergents in them, so sludge will be broken up, and can get stuck in oil galleys or pumps or filters. Also, as far as leaks go, OLD engines (pre-1987 for most mopar engines) did not have a synthetic gasket set in them so stay away from high detergent synthetics (Mobil 1 is about the worst for old engines, but the best for newer engines). The problem from switching oils IS NOT going from Conv--->Syn it is the other way around. When you run synthetic, your gaskets will expend beyond their original size and stay that way, if you switch back to conventional, they will begin to shrink, and eventually become about 1/2 as large as original spec. If you have ever seen a newer vehicle with low miles burn oil, this is usually why. Also, thos oil additives you often see to stop oil burning are synthetic conditioners which only increase seal and gaskets sizes, if you then change your oil and don't run synthetic or the additive again, you can only expect another 20-30k miles out of those gaskets and seals. All of this information was given to me by one of the lead engineers from Mobil Oil who told me he has never changed the synthetic oil in his 1998 Dodge Ram Beater, he simply filters the oil (his own process), and changes the filter every 5K miles. Synthetic oil gets dirty, but it never breaks down.