Lubricating oil having improved fuel economy retention properties

A lubricating oil composition exhibiting improved fuel economy and fuel economy retention properties which comprises an oil of lubricating viscosity containing (a) 0.3 to 6% by weight of an overbased oil soluble calcium detergent additive and (b) an oil soluble tri-nuclear molybdenum compound of the formula Mo.sub.3 S.sub.k L.sub.n, where k is 4-10, n is 1-4 and L is an organic ligand having sufficient carbon atoms to render the molybdenum compound oil soluble, said ligand being selected from the group consisting of:

• xanthate, thioxanthate, dialkylphosphate, dialkyldithiophosphate, dialkyldithiocarbamate, carboxulate, and a mixture thereof, said molybdenum compound being present in such an amount as to provide 10-1000 ppm molybdenum in the composition.