The invention discloses energy-efficient long-life gasoline engine oil prepared from the following components: synthetic base oil, a composite antioxygen, a metal cleaning agent, an ashless dispersant, a nano-level friction improver, a viscosity improver and a pour point reducer. The gasoline engine oil provided by the invention has the following advantages: requirements of API SM, ILSAC GF-4 and SAEJ300 are met and the service life is long; the complete synthetic base oil features low pour point, high viscosity index, good economy of fuel, degradability and reduced harm to the ecological environment; the phenol type antioxygen is combined with ZDDP, the anti-oxygen and antifriction properties are good and the catalyst poisoning in a tail gas processing unit is prevented; the acid neutralization capacity is good, the cleaning dispersibility is good and the oil sludge and carbon deposit are prevented from being generated; and the nano-level friction improver is added, the frictional factor is low, and the oil film features high carrying capacity and can automatically repair abraded surface and lengthen the service life of the engine.