I did a little research on M1 EP 5W-20 and found that the specs are interesting when compared to Amsoil 0W-20. The specs for M1 do not look all that bad. Though I am no expert, some M1 specs even seem to surpass the Amsoil specs. I understand that M1 does not list all of the items Amsoil does, perhaps that is where the big difference is found and where Amsoil shines?
Mobil 1 Extended Performance:
SAE Grade: 5W-20
Viscosity, ASTM D 445
cSt @ 40ºC: 47.4
cSt @ 100ºC: 8.9
Viscosity Index: 171
Sulfated Ash, wt%: 1.0
HTHS Viscosity, mPa·s @ 150ºC: 2.7
Pour Point,ºC: -51
Flash Point,ºC: 235
Density @15º C kg/l: 0.86
AMSOIL 100% Synthetic 0W-20 Motor Oil (ASM)
Viscosity @ 100°C: 9.0
Viscosity @ 40°C: 49.1
Viscosity Index: 165
VISC. CCS,cP: 4069 (-35)
Flash Point °C (°F): 228 (442)
Fire Point °C (°F): 246 (475)
Pour Point °C (°F):-54 (-65)
NOACK (% weight loss): 8.6
Four Ball Wear, 75°C, 1200 rpm, 40kg, 1 hour: 0.35
Total Base Number: 12.1
High Temperature/High Shear Viscosity
(ASTM D-4683 @ 150°C, 1.0 X 106 s.-1): 2.8
Mobil 1 Extended Performance:
SAE Grade: 5W-20
Viscosity, ASTM D 445
cSt @ 40ºC: 47.4
cSt @ 100ºC: 8.9
Viscosity Index: 171
Sulfated Ash, wt%: 1.0
HTHS Viscosity, mPa·s @ 150ºC: 2.7
Pour Point,ºC: -51
Flash Point,ºC: 235
Density @15º C kg/l: 0.86
AMSOIL 100% Synthetic 0W-20 Motor Oil (ASM)
Viscosity @ 100°C: 9.0
Viscosity @ 40°C: 49.1
Viscosity Index: 165
VISC. CCS,cP: 4069 (-35)
Flash Point °C (°F): 228 (442)
Fire Point °C (°F): 246 (475)
Pour Point °C (°F):-54 (-65)
NOACK (% weight loss): 8.6
Four Ball Wear, 75°C, 1200 rpm, 40kg, 1 hour: 0.35
Total Base Number: 12.1
High Temperature/High Shear Viscosity
(ASTM D-4683 @ 150°C, 1.0 X 106 s.-1): 2.8