viscosity temprature chart help you in choosing good motor oil
Viscosity is depedent on temprature.It is inversely proportional to temprature.It means that if you increase the temprature,the viscosity will decrease.
You can see from your daily experience that liquids flow easily when heated.For example hot honey will flow more smoothly in comparison to honey at normal temprature.Hence the motor oil thickens on cold days and your car performence is affected.Similarly on a hot day,motor oil will flow more smoothly.You can decide on the perfect viscosity of your motor oil as you know the climate conditions in your locality.SAE grades help you in choosing motor oil.