Prediction of Viscosity Stability of Multigrade Engine Oils in Service

The viscosity change of multigrade motor oils in service has been evaluated in a fleet representative of the present European car population. The evaluation covered air- and water-cooled engines, with conventional and integral gearboxes, and displacements ranging from 500-1750 cc.

The effect of car, service, average ambient temperature, and type of polymer on the viscosity change of a lubricant has been estimated.

The multigrade test oils have also been run in injector and bench engine tests in order to compare field testing results with laboratory techniques being developed.