Cylinder lubricating oil composition for crosshead diesel engine

A cylinder lubricating oil composition for a crosshead diesel engine, the composition having:

• a sulfated ash content of 2.0 to 5.5 mass %;
• a base number of 15 to 45 mgKOH/g;
• a kinematic viscosity at 100° C. of 12.5 mm2/s or more;
• and
• an autoignition temperature of no less than 262° C., wherein the autoignition temperature is determined by means of pressurized differential scanning calorimetry as a temperature at which the composition begins to generate heat when 3 mg of the composition is heated in an oxygen atmosphere at a pressure of 1.0 MPa from 25° C. to 500° C. at a heating rate of 10° C./min,
• the composition comprising:
• a lubricant base oil;
• (A) at least one of
• a Ca salicylate detergent having a metal ratio of no more than 7 or
• a Ca phenate detergent having a metal ratio of no more than 7;
• (B) a Ca sulfonate detergent having a base number of no less than 10 mgKOH/g and less than 60 mgKOH/g;
• (C) a Ca phenate detergent having a base number of 55 to 200 mgKOH/g;
• (D) at least one of
• an amine antioxidant or
• a sulfur-containing compound;
• and
• (E) a zinc dithiophosphate or a zinc dithiocarbamate,
• wherein the sulfur-containing compound is a compound other than a metallic detergent, a zinc dithiophosphate, a zinc dithiocarbamate, an oil-soluble organic molybdenum compound, and an ashless detergent;
• and
• the lubricant base oil consists of one or more selected from the group consisting of Group I base oil of API base stock categories and Group II base oil of API base stock categories.