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.
"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
