Lubricating oil composition in contact with silver-containing material

A lubricating oil composition in contact with a silver-containing material, which comprises:

• a lubricant base oil made of a hydrocracked mineral base oil and/or a poly-α-olefin, sulfur content in said lubricant base oil being less than 50 ppm;
• (A) one or more metallic detergent selected from the group consisting of calcium phenate, calcium sulfonate, and calcium salicylate;
• (B) one or more species of alkenyl succinimide and/or boron-containing alkenyl succinimide;
• and
• (C) zinc dialkyl dithiophosphate, wherein the content of these components to the total mass of the lubricating oil composition are defined as,
• (A) component:
• 0.15-0.4 mass % as metal content;
• (B) component:
• 0-0.03 mass % as boron content, 0.005 mass % to 0.07 mass % as nitrogen content, and the mass ratio (B/N) between the boron content (B) and the nitrogen content (N) is 0-0.55;
• and
• (C) component:
• 0.02-0.10 mass % as phosphorus content, and mass ratio (M/N) between the metal content (M) attributed to the (A) component and the nitrogen content (N) attributed to the (B) component is 3.0 to 8.4.