| 摘要 |
PROBLEM TO BE SOLVED: To provide a base oil for a four-cycle engine oil having a characteristic of stably retaining an oil film under a severe condition for a long time without compounding an additive, and showing extreme excellence in rocker arm pad scuffing prevention performance, a camshaft abrasion prevention performance and a camshaft pitching prevention performance. SOLUTION: This base oil for the four-cycle engine oil includes (A) 10 to 90 mass%, based on the whole amount, of an ester-based lubricant base oil (A), and 90 to 10 mass% of a mineral oil-based lubricant base oil and/or a poly-α-olefin-based lubricant base oil (B) wherein the ester-based base oil (A) is composed of 5-30 mass% of a copolymer (A-1) of a dicarboxylate and a 3-20Cα-olefin having a dynamic viscosity of 20-50 mm<SP>2</SP>/s at 100°C, and 5 to 60 mass% of an ester (A-2) of a polyhydric alcohol and a fatty acid having a dynamic viscosity of 2-50 mm<SP>2</SP>/s at 100°C. COPYRIGHT: (C)2011,JPO&INPIT |
