Look at the testing parameter differences in these two Amsoil 30wts .
Now why does Amsoil do this ?
That one is - Four-Ball Wear Test (ASTM D 4172: 40kgf, 150°C, 1800 rpm, 1 hr) Scar diameter, mm
And for the second oil - Four Ball Wear Test
(ASTM D-4172B: 40 kgf, 75°C, 1200 rpm, 1 hr), Scar, mm