Phosphorus-comprising lubricating oil composition

A lubricating oil composition comprising a phosphorous compound having two or more hydroxyl groups and a P—N bond in a molecule (simply abbreviated as “First Phosphorous Compound”), and one or more phosphorus compounds (simply abbreviated as “Second Phosphorus Compound”) wherein,

• said First Phosphorous Compound is represented by the general formula (1) or (2):
• wherein R1 and R2, which may be identical or different, each represents a linear or branched alkylene group having 2 to 4 carbon atoms;
• p and q are from 0 to 30;
• and R3 and R4, which may be identical or different, each represents a hydrogen atom;
• a linear alkyl group having 1 to 30 carbon atoms;
• a branched alkyl group having 3 to 30 carbon atoms;
• a linear alkenyl group having 2 to 30 carbon atoms;
• a branched alkenyl group having 3 to 30 carbon atoms;
• an aryl group having 6 to 30 carbon atoms;
• an aralkyl group having 7 to 30 carbon atoms;
• a halogenated alkyl group having 1 to 30 carbon atoms;
• or a halogenated aryl group having 6 to 30 carbon atoms, provided that when p is 0, R3 is not a hydrogen atom, or when q is 0, R4 is not hydrogen atom;
• and
• said Second Phosphorous Compound is selected from the group consisting of compounds represented by the general formula (3)
• wherein R1 to R5 and R7 to R9, which may be identical or different, each represents an aryl group having 6 to 18 carbon atoms;
• a linear alkyl group having 1 to 18 carbon atoms;
• a branched alkyl group having 3 to 18 carbon atoms;
• a linear alkenyl group having 2 to 18 carbon atoms;
• or a branched alkenyl group having 3 to 18 carbon atoms;
• and R6 represents a hydrogen atom;
• a linear alkyl group having 1 to 18 carbon atoms;
• a branched alkyl group having 3 to 18 carbon atoms;
• a linear alkenyl group having 2 to 18 carbon atoms;
• or a branched alkenyl group having 3 to 18 carbon atoms;
• and wherein said lubricating oil composition comprises, based on 100 parts by weight of a lubricating base oil, 0.001 to 5.0 parts by weight of said First Phosphorus Compound and 0.1 to 5.0 parts by weight of said Second Phosphorus Compound.