At Checker I see they sell SAE 30 SAE 40 oil. Why couldn't one use a SAE oil in summer? M1 15w50 says it pumps at -39f and its pour point is -45. 5w30 pour point is -39. Why wouldn't I use it in winter??? http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_Drive_Clean_Oils.asp Typical Properties Mobil 1 15W-50 SAE Grade 15W-50 Viscosity, ASTM D 445 cSt @ 40º C 125 cSt @ 100º C 17.4 Viscosity Index, ASTM D 2270 153 Sulfated Ash, wt%, ASTM D 874 1.3 HTHS Viscosity, mPa·s @ 150ºC ASTM D 4683 5.11 Pour Point, ºC, ASTM D 97 -45 Flash Point, ºC, ASTM D 92 230 Density @15º C kg/l, ASTM D 4052 0.864 I wounder if I went to a M1 15w50 I would still suck oil at high rpms like M1 0w40 and M1 10w30 does?