Check out this guy's page: https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/ I've switched to this: 73. 20W50 Castrol GTX, API SN conventional = 96,514 psi zinc = 610 ppm phos = 754 ppm moly = 94 ppm from O'Reilley's 20w-50. GTX lasts a lot longer than the o'Really?s stuff; I had that stuff tapping out after one trip into Minneapolis and back. My gauge on how the oil is doing is how bad the shifting has degraded, and since late last summer, I can't tell any degradation on the GTX. Serious improvement.