Dispersing agent for lubricating oil, method for producing same, and lubricating oil composition

A dispersant for a lubricating oil, comprising at least one compound selected from a nitrogen-containing compound represented by any one of the following formulae (1) to (4), which is obtained by using, as raw materials,

• (A) at least one polyolefin selected from polybutene and polyisobutene,
• (B) at least one maleic acid compound selected from maleic acid and maleic anhydride, and
• (C) polyamine;
• a boride of the nitrogen-containing compound;
• and
• an acylated product of the nitrogen-containing compound:
• wherein each of R1, R3, R4, R7, and R9 is independently an alkenyl group selected from a polybutenyl group and a polyisobutenyl group, or an alkyl group selected from a hydrogenated polybutenyl group and a hydrogenated polyisobutenyl group;
• wherein a molecular weight distribution (Mw/Mn) of the alkenyl group and the alkyl group is 1.80 or less, and a mass average molecular weight (Mw) of the alkenyl group and the alkyl group is 500 to 5,000;
• wherein each of R2, R5, R6, R8, R10, and R11 is independently an alkylene group having 2 to 5 carbon atoms;
• wherein each of m, n, p, q, and r is independently an integer of 1 to 10, and
• wherein the at least one polyolefin (A) satisfies at least one of the following conditions (α) and (β):
• (α) a ratio (Sb/Sa) of an integrated value (Sb) of a peak present at 4.40 to 5.00 ppm in a 1H-NMR spectrum to an integrated value (Sa) of a peak present at 5.01 to 5.60 ppm in the 1H-NMR spectrum is 2 or more;
• and
• (β) a ratio (Sd/Sc) of an integrated value (Sd) of a peak present at 1.76 to 2.10 ppm in the 1H-NMR spectrum to an integrated value (Sc) of a peak present at 1.65 to 1.75 ppm in the 1H-NMR spectrum is 1 or more.