I have been having some email discussions with the Engineer at ZDDP. I told him that I had some extra bottles of ZDDP on my shelf and that I would be adding the Brad Penn Grade 1 oil and I was wanting to know if I needed to add the ZDDP even though I have notes showing that the Z/Ph averages on this oil are 1400-1600ppm (depending on source). He told me that he likes to see street engines stay at 2000ppm or less of Phosphorous and he stated that if my BP oil did average 1400ppm, then I was to ONLY add 1-1.5 ouces of the ZDDP product. This small amount would put me in the 1714/1870 range. He also said that if my average was at the 1600ppm mark, then he said no more than 1 ounce would give me a phos number of around 1900ppm.
I just wanted to throw this out there.