| abstract |
This lubricating-oil composition comprises the following: a base oil that contains at least one mineral oil and/or synthetic oil, has a viscosity index of at least 120, and has a paraffin content, as per ring analysis, of at least 70%; a dispersant (A) containing at least one compound selected from among alkenyl succinimides, boronated alkenyl succinimides, alkyl succinimides, and boronated alkyl succinimides; and a metallic cleaning agent (B) containing at least one compound selected from among alkali-metal sulfonates, alkali-metal phenates, alkali-metal salicylates, alkaline-earth-metal sulfonates, alkaline-earth-metal phenates, and alkaline-earth-metal salicylates. Component (A) contains 0.01-0.10 mass% of the total nitrogen content of the composition, and component (B) contains 0.01-0.3 mass% of the total metal content of the composition. Component (A) contains at least one compound selected from among boronated alkenyl succinimides and boronated alkyl succinimides. The B/N ratio of component (A), i.e. the mass ratio between the boron content and the nitrogen content thereof, is at least 0.5. The phosphorus content of the entire composition is between 100 and 1,200 mass ppm, inclusive, and the sulfated-ash content of the entire composition is at most 1.1 mass%. This makes it possible to combine engine performance with engine durability by preventing performance losses in vehicular internal combustion engines that can produce higher output and better fuel economy due to higher thermal and mechanical temperature tolerances than traditional engines. |