US Patent 7790659 Lubricating oil compositions

Disclosed are lubricating oil compositions excellent in friction reducing effect and long drain properties and particularly suitable for internal combustion engines, which comprise a lubricating base oil, a specific phosphorus compound in an amount of 0.005 to 0.5 percent by mass in terms of phosphorus based on the total mass of the composition, and at least one additive selected from the group consisting of (C) metallic detergents, (D) ashless dispersants, and (E) anti-oxidants, and further contains (F) a sulfur-containing organic molybdenum complex and (G) an ashless friction modifier and which satisfy prescribed requirements and have a sulfated ash content not exceeding a specified level.