Lubricating oil composition

A method for producing a lubricating oil composition, the method consisting of blending at least one base oil with a mixture consisting of:

• a 2,6-di-tert-butylphenol (A) and optionally at least one other phenol-based antioxidant;
• a sorbitan compound (B);
• optionally at least one benzotriazole compound;
• at least one phosphorus-containing extreme pressure agent (C);
• and
• optionally at least one succinate compound (D)
• optionally at least one amine-based antioxidant (E);
• and
• optionally at least one additive selected from the group consisting of an ash-free dispersant, a viscosity index improver, a pour point depressant, a defoaming agent, a rust inhibitor, a metal inactivator and mixtures thereof, to obtain the lubricating oil composition,
• wherein:
• the lubricating oil composition has a kinematic viscosity at 40° C. of 20 to 500 mm2/s,
• the lubricating oil composition does not contain a metal detergent;
• and
• the at least one base oil includes at least one mineral oil which is grouped in Group 2 or 3 in the base oil category of API (American Petroleum Institute) as a major amount of the at least one base oil;
• a content of the base oil is 80 to 99.7% by mass, based on the total amount of the lubricating oil composition;
• a content of the 2,6-di-tert-butylphenol (A) is 0.2 to 1.0% by mass, based on a total amount of the lubricating oil composition;
• a content of the sorbitan compound (B) is 0.02 to 0.2% by mass, based on the total amount of the lubricating oil composition;
• the sorbitan compound (B) includes at least a sorbitan monooleate (B1);
• and
• the ratio by mass of the sorbitan monooleate (B1) to the 2,6-di-tert-butylphenol (A) (B1/A) is from 0.005 to 0.3;
• the phosphorus-containing extreme pressure agent (C) is at least one selected from the group consisting of a triaryl phosphate, a dithiophosphate and a phosphate amine salt;
• when the phosphorus-containing extreme pressure agent (C) is a phosphate amine salt, a content of the phosphate amine salt is 0.01 to 0.08% by mass, based on the total amount of the lubricating oil composition;
• when the phosphorus-containing extreme pressure agent (C) is at least one of a triaryl phosphate and a dithiophosphate, a content of the phosphorus-containing extreme pressure agent (C) is 0.1 to 1.5% by mass, based on the total amount of the lubricating oil composition;
• when the lubricating oil composition is tested with a Falex test machine, where a pre-conditioning interim operation is carried out at 1334 N and 290 rpm for 5 minutes, and then under continuous loading of 40 N/sec at 25° C., the load until seizing is 3120 N or more;
• when a rotating pressure vessel oxidation test based on JIS K2514 is performed on the lubricating oil composition at 150° C., the time (RPVOT Value) is takes for the vessel pressure to lower by 175 kPA from the maximum pressure before the start of the test is 606 minutes or more;
• when the lubricating oil composition is tested according to the method described in ASTM D7873-13, the amount of sludge formation measured using a membrane filter having a mean pore size of 1.0 μm after 480 hours is 0.4 mg/100mL or less.