I'm not really good at some mechanical stuff. The price difference between ZR-1 and conventional isn't that much of a difference. I did stop by NAPA and talked to a guy in there and he said high mileage has more zinc, but according to Valvoline online high mileage (max life) has zinc/phosphorus% of .083/.077, conventional is .083/.076, and ZR-1 is .14/.13. Looks like ZR-1 has the most. I don't have the mechanical know how on lots of things, but wish I had learned more when my dad was working on cars. I usually take it to someone to get stuff done if I can't figure it out. I could call the shop that works on it and see if they know from what they've done on it. I wouldn't even know what to look for if I took off a valve cover to be honest.