1600ppm would be 0.16% Did I beat the rocket scientist? David L 2009/7/20 Billy Zoom <billyzoom at billyzoom.com>: > As I understand it, original ZDDP level was 1600ppm, which was lowered to > 800ppm in 1987, and down to 400ppm recently. I don't know what means as a > percentage. Maybe some rocket scientist will chime in.