Typical oil analysis use atomic mass spectroscopy. There are various methods of performing this analysis, but the results are the same: The relative mass ratios of constituent atoms are measured. This means that in the case of Zn, the relative strength of the Zn reading is due to the TOTAL zinc in the original sample. This total Zn includes atomic Zn that is in the oil PLUS the Zn in the zinc oxide which some oil incorporates as an acidity buffer, PLUS the Zn which was a constituent of the ZDDP...
Only the Zn that is incorporated into the ZDDP molecule acts as an EP agent, so the atomic mass of all of the Zn is not an accurate measure of the ZDDP content.
There are other techniques for analyzing the molecular makeup of oil that can pinpoint the ZDDP molecule as opposed to the atomic Zn or P in the oil. One method is the FTIR (Fourier Transform InfraRed) Spectroscopy. There is a good write up on the advantages of this technique in the Sept/Oct issue of the Practicing Oil Analysis Magazine.
Molecular Spectroscopy - A Precision Lubrication Tool?
We will be posting actual ZDDP molecular test results for ZddPlus as well as a few other "lubrication products" soon. As usual, a thinking person should be skeptical of any product claims that are unsupported by actual test results, preferably multiple test results. Remember; current oil formulations are rapidly changing, and the Zn and P levels are a moving target. We believe that a test more than 90 days old needs to be viewed as a questionable representation of the currently available oil formulation.