I have a 1988 4X4 with 150K on it....It had the head gasket replaced at 120 K..It has a tick from the engine. Sounds like valve lash or exhaust leak..I was thinking of using a long screwdriver to try to listen to the valve train...The head was re-torqued after 1000 miles on the new gasket...My Mechanic just wants to go to 15W 40 Rotella ...He said that would stop the tick...If it is an exhaust leak, I could care less as it is a fairly tight cab with lots of flow thru , lots of air to move the gases along and it will soon need new muffler type stuff soon.( lots of macho sound)...It got a new exhaust manifold when the gasket was replaced, but may be bad again.....Please comment on the 15 W 40 Rotella....Ideas?

Charlie