| abstract |
The present invention provides a system lubricating oil composition for a crosshead-type diesel engine, which can prevent fuel efficiency deterioration by suppressing the viscosity increase and comprises a mineral base oil and/or a synthetic base oil, (A) (a-1) a star polymer having a vinyl aromatic hydrocarbon structure in the molecule and/or (a-2) an ethylene-α-olefin copolymer or a hydrogenated compound thereof and having a base number of 4 to 20 mgKOH/g and a 100°C kinematic viscosity of 7.5 to 15.0 mm 2 /s. |