WE run Kendall GT1 in all our motors.I have full synthetic in the 440 now because I got Valvoline syn race free.Mines been in 10 years as has the kids.My.588 solid has no problems and his was still running the 62 cam till we put the Hughes in.Come to NE Ohio there are still a ton of lod junkers running flat tappets that drive everyday with no problems.Both our cars are street driven and raced.Changing oil and making sure the lifters rotate are the most important thing.Rocky