Anyone else notice how nearly identical the specs are on these two oils? http://www.amsoil.com/products/afl.htm http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil1_0W-40.asp M1 T&SUV is quite a bit thicker on the cold end. http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_Truck_SUV_5W-40.asp With this in mind, I would think the Amsoil would be a better oil since the M1 0w-40 likes to thin out and the M1 5w-40 is quite a bit thicker at startup.