So far it is. I did a camshaft synchronizer about 25k miles ago and will do it again in 25k or so. Been on Rotella SB 10w30 for a long time and it is getting switched to Schaeffer 5w40 when that runs out. Hot heat, cold air and 26mpg on the highway. Went through the cooling system a couple years ago as the hoses and water pump were original. Did WP, thermostat, all hoses, and heater core and put new G-05 in.