Oil Viscosity influences chain slap on SL (e.g. 380SL)

[ericgr]

In a post about a month ago I indicated that my car, a 380SL with new chain/tensioner/rails/etc put in about 2 years ago had developed an occassional chain slap. I also guessed that it may have been related to oil viscosity since the chain tensioner in these cars is hydraulic. To verify the guess, I changed the oil from a very heavy 20w-50 in there (I really didn't need that heavy a viscocity, I had just done it for one oil change) to Mobile One synthetic 10w-30. Since making that oil change, there has never been any indication of chain slap. So if you have a car that has no reason to have chain slap but does, you might consider changing the oil to a lighter weight one and, if you believe in synthetic for your car, maybe a synthetic one. I have come full circle on the use of synthetic oil for the moment and will continue to use it and monitor any significant increase in oil leakage.