Whats the difference between parts per million (PPM) and WT% when measuring the zinc content in motor oil? For instance the zinc content in Lucas 20-50 "racing only" dino oil is expressed as: 3,132 PPM. In Valvoline NSL 20-50 synthetic its expressed as ZNWT% 0.14. Is it possible to convert the % as expressed in the Valvoline oil to PPM or PPM to WT%? Any insight appreciated.