Normal conditions, mostly highway mileage he had an hour Interstate drive to work. No modification, no drag racing. The car had about 40 or
50K miles on it. On the first oil change I went to RP and inside of a week I started seeing what looked like flakes of varnish on the dip stick. A couple of years later when I replaced the heads and intake I saw what it was. The non-wear surfaces of the cam looked like it had a thin layer of shellac on it. Since the previous owner used Syntec since day one and I changed to RP and it cleaned it, one can only assume the Syntec left the crap layer behind.after the 2nd or 3rd RP change it had stopped and somewhere after that I switched to Amsoil. I guess that side effect of RP can be really good IF you know about it and keep it in check and if you don't have some sludge/varnish that is plugging a hole.Oh, the valve covers were horrendous as well, I had to chisel the crap out with a screwdriver. They looked almost as bad as a 60K mile Pennzoil set of valve covers used to if you used it in the 70s.