| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a viscosity index improver which has a high viscosity index improving effect and does not easily increase low-temperature viscosity of a lubricating oil composition.SOLUTION: The viscosity index improver contains a (co)polymer (A) comprising a polymerizable unsaturated group-containing macromonomer (Y) represented by the specified general formula (1) as an essential constituent monomer, where the absolute value of the difference in solubility parameters of (Y) and (A) is 0.5 to 1.2.</p> |
