Does the viscosity @ 40 Celsius determine an oil rating of 0W, 5W, 10W etc? Here are some oil specs @ 40C: Mobil1 0W-40: 80.3 cSt RedLine 5W-40: 94 cSt Amsoil 10W-40: 79.2 cSt From the above, the Amsoil should flow the best at lower temperatures. Why is it a 10W and the thicker Redline a 5W? Would the Mobil1 or RedLine flow better than Amsoil at 10C? 0C?