Brad Penn utilizes the ASTM qualified lab, Southwest Research Institute (SwRI), for additive element testing and reporting. There again, SwRI uses the industry standardized test method, ASTM D5185 (ICP), to determine zinc content of lubricant oils.
As such, Penn Grade 1 oils have between 1540-to-1565 ppm zinc content.
For more on Southwest Research Institute (SwRI), click on the link - HERE
SWRI does good research and is a reputable institute, but ICP-AES simply isn't as accurate as NAA (it's only the "industry standard" because NAA typically requires access to a nuclear reactor). You will literally not find a single paper in a peer-reviewed scientific journal that claims that ICP-AES is a more sensitive method of trace element analysis than NAA.
And how minute would be the difference and would it really matter ?
That's a good question and not an easy one to answer. The uncertainties in all of the numbers that we obtained using NAA were less than 1%. I very rarely see ICP-AES data that includes uncertainties and goes into any detail concerning how they were calculated. I would estimate that the ICP-AES data related to motor oil analysis typically have uncertainties of about 5%, but my estimate is only based on ICP-AES uncertainties associated with analysis of other materials, so take that estimate with a grain of salt. They could be better, or they could be worse.
"When I'm in a slump, I comfort myself by saying if I believe in dinosaurs, then somewhere, they must be believing in me. And if they believe in me, then I can believe in me." - Mookie Wilson
