ThE VISCOSITY AND GRADES OF A LUBRICANT OIL VISCOSITY OIL GRADES The viscosity of a lubricant, which is its capacity to flow, is dertermined by its grade. It is indicated by two separated num- bers by a letter W which stands for Winter.
The SAE (Society of Automotive Engineers) has created a classi- fication for lubricant grades in order to characterize viscosity at high and low temperatures.
The grades are stated as follows :
Sae xxW or Sae yy Monograde lubricant
(ex : 10W, 30, 40)
Sae xxW-yy Multigrade lubricant (ex : 5W-30, 15W-40)
The higher the number, the higher the viscosity level.
COLD GRADE hOT GRADE
1st number = cold grade the lower the number is, the more fluid at cold the lubricant is.
2nd number = hot grade the higher the number is, the more viscous at hot the lubricant is.
easy start at low temperature
engine protection at high temperature
xx indicates viscosity at cold temperatures
(measured at different temperatures)
yy indicates viscosity at hot temperatures
(measured at 100°C and 150°C)
xx w - yy