Here's what is stated in the API SP specifications. It states that phosphorus must be between 0.06-0.08% (600-800 ppm). It then gives footnotes, one stating it doesn't apply to non-ILSAC grades (ie: 10W-40, 20W-50), and the other referring to ASTM D3244 as the specification being non-critical.
Here's an excerpt from ASTM D3244, the conformance of critical vs non-critical specification.
What I take this to mean is that phosphorus can be below the 0.06% (600 ppm) minimum so long as the oil still passes the anti-wear tests.
Here's an excerpt from ASTM D3244, the conformance of critical vs non-critical specification.
What I take this to mean is that phosphorus can be below the 0.06% (600 ppm) minimum so long as the oil still passes the anti-wear tests.