AUTOMOTIVE GEAR LUBRICANT VISCOSITY CLASSIFICATION

The following descriptions in the categories in the API Engine Service Classification System are intended as guides to aid in the selection of proper engine oils for significantly different engine service conditions. The performance requirements for these categories are technically described on the API Web site

The classification is based on the lubricant viscosity measured at low and/or high temperatures. Athe high temperature values are determined according to method ASTM D445. The low temperature values are determined according to method ASTM D2983 “Method of  Test for Apparent Viscosity at Low temperature using the Brookfield Viscometer”and are measured in mPa.s (CP).

A multigrade oil satisfies the viscosity requirementsof one of the W grades at low temperature and
one of the non-W grades at high temperature

SAE Viscosity Grade

Maximum  Temperature (°C ) for Viscosity of 150,000 m Pa s (ASTM D2983)

Viscosity at 100°C
(ASTM D445)

min

max

70W

-55

4.1

75W

-40

4.1

80W

-26

7.0

85W

-12

11.0

90

13.5

24

140

24.0

41

250

41.0