Patent ID: 8728999

Claim:
A method for improving the fuel economy of large low and medium speed engines that reach surface speeds of at least 3 mm/s and are lubricated by an engine oil by reducing the traction coefficient of the engine oil used to lubricate the engine by employing as the engine oil a lubricating oil having a kinematic viscosity at 100° C. of about 20 to 25 mm 2 /s comprising a base oil comprising a bimodal blend of two different base oils, the first base oil being one or more oils selected from the group consisting of Group I base oils having a kinematic viscosity at 100° C. of from 4 to 8 min 2 /s and a second base oil selected from one or more oils selected from Group IV base oils having a kinematic viscosity at 100° C. of 38 mm 2 /s to 150 mm 2 /s, and containing one or more detergents selected from the group consisting of alkaline earth metal sulfonate, salicylate, carboxylate, salicylate/sulfonate, phenate/salicylate, phenate/sulfonate, and phenate/carboxylate in an amount in the range of 6 to 30 wt % based on active ingredient wherein the improvement in the fuel economy is evidenced by the engine oil having a coefficient of traction which is lower than the coefficient of traction as compared to engine oils which are not bimodal or which are based on Group I base oils or mixtures of Group I base oils and PIB.