28. “ZDDPlus” added to Royal Purple 20W50, API SN, synthetic = 63,595 psi zinc = 2436 ppm (up 1848 ppm) phos = 2053 ppm (up 1356 ppm) ZDDP = 2200 ppm
The amount of ZDDPlus added to the oil, was the exact amount the manufacturer called for on the bottle. And the resulting psi value here was 24% LOWER than this oil had BEFORE the ZDDPlus was added to it. Most major Oil Companies say to NEVER add anything to their oils, because adding anything will upset the carefully balanced additive package, and ruin the oil’s chemical composition. And that is precisely what we see here. Adding ZDDPlus SIGNIFICANTLY REDUCED this oil’s wear prevention capability. Just the opposite of what was promised. Buyer beware.