I ran 15w-50 M1 for a 4,000 mile oil change interval. The actual zinc and phosphorus in the used oil analysis was way below what is specified by Mobil. 1013 zinc/889 phos. Mobil specs 1300/1200. Could have been an anomaly however it still was a solid 40 weight. M1 10w40 4T was slightly higher on the sus vis at 5,345 mi, zinc (1204) was just under what Mobil specs (1300 ppm) however phosphorus was 987 with spec of 1200 ppm.