Check out www.bobistheoilguy.com There's lots of info that supports not using additives that could compromise the original formula an oil was designed with. I use Brad Penn 1 Racing oil in my hemi & its a great oil w/ 1300+ PPM Zinc & over 1200 PPM of Phosphorous. And its only partial synthetic. Valvoline VR1 also is high in zinc & highly recommended. Check out www.bradpennracing.com
