Categories of oil viscosity set up by the Society of Automotive Engineers （SAE）. The number followed by “W” means the viscosity grade under low temperature conditions （by CCS viscosity or Pumping viscosity; MRV） and the lower the number, the better the cold startability becomes. A number without “W” means the viscosity grade under high temperature conditions （by kinematic viscosity at 100ｰ℃） and the larger the number, the higher the viscosity becomes.