Patent ID: 8748362

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 up to 100 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 comprising a base oil comprising a bimodal blend of two different base oils, a first base oil being one or more oils selected from the group consisting of Group IV base oils, which first base oil has a kinematic viscosity at 100° C. of about 6 mm 2 /s, and a second base oil being one or more oils selected from Group IV base oils having a kinematic viscosity at 100° C. of about 150 mm 2 /s, the difference in kinematic viscosity between the first and second base oils in the blend being at least 140 mm 2 /s, the combination of the first and second base oils having a kinematic viscosity at 100° C. of about 9 mm 2 /s or less, the lubricating oil further containing about 1.08 to 1.95 wt % based on active ingredient of a detergent selected from a calcium salicylate or a mixture of calcium phenate and calcium salicylate, wherein the improvement in fuel economy is evidenced by the engine oil having a traction coefficient which is lower than the traction coefficient of engine oils which are not bimodal or which are not bimodal to the same degree as recited or which are based on Group I and/or Group II base oils, and which do not contain the aforesaid detergents.