polymer causes more thickening at high temperatures, giving the oil "multigrade" characteristics. This is illustrated schematically in Fig.3. "Multigrade" oils fall into a higher viscosity band at l00°C than that of the straight "W" grade oil. For example, a SAE 10W40 oil has a viscosity of less than 3500 cP at -20°C but must have a viscosity greater than 12.5 cSt (about 10.5 cP) at 100°C, rather than 4.1 cSt for a SAE I0W oil