Lubricant composition
The invention provides a lubricating oil composition being a lubricating oil composition containing a base oil composition which includes a lubricant base oil belonging to Group 3 of the base oil categories specified by the American Petroleum Institute (API) and a comb-like polymethacrylate-based viscosity index improver wherein the weight-halving temperature is not less than 310° C., and the sulphur content in the aforementioned lubricating oil composition is not more than 0.3 weight % in terms of the total weight of the aforementioned lubricating oil composition, and the aforementioned lubricating oil composition has an SAE viscosity grade of 0W-20, 5W-20 or 5W-30, a viscosity index of not less than 185 and a high-temperature high-shear viscosity at 100° C. of not more than 7.5 mPa·s.
1. A lubricating oil composition comprising:
(a) a base oil composition comprising a lubricant base oil belonging to Group 3 of the base oil categories specified by the American Petroleum Institute (API); and
(b) a comb-like polymethacrylate-based viscosity index improver having a weight-halving temperature of at least 310° C., and
wherein the lubricating oil composition has
a sulphur content of at most 0.3 weight % in terms of the total weight of the lubricating oil composition,
an SAE viscosity grade of 0W-20, 5W-20 or 5W-30,
a viscosity index of at least 185, and
a high-temperature high-shear viscosity at 100° C. of at most 7.5 mPa·s.
2. The lubricating oil composition in accordance with claim 1 wherein the viscosity index of the base oil composition is at least 120.
3. The lubricating oil composition in accordance with claim 1 wherein a % Cp of the base oil composition on the basis of ASTM D3238 is at least 90%.
4. The lubricating oil composition in accordance with claim 1 wherein the weight-halving temperature of the comb-like polymethacrylate based viscosity index improver is at least 320° C.
5. The lubricating oil composition in accordance with claim 1 wherein the sulphur content of the lubricating oil composition is at most 0.25 weight % in terms of the total weight of the lubricating oil composition.
6. The lubricating oil composition in accordance with claim 1 wherein a sulphated ash content of the lubricating oil composition is at most 0.6 weight % in terms of the total weight of the lubricating oil composition.
7. The lubricating oil composition in accordance with claim 1 wherein the comb-like polymethacrylate-based viscosity index improver comprises at least 70% methacrylate.
8. The lubricating oil composition in accordance with claim 7 wherein the viscosity index of the base oil composition is greater than 120.
9. The lubricating oil composition in accordance with claim 7 wherein a % Cp of the base oil composition on the basis of ASTM D3238 is at least 90%.
10. The lubricating oil composition in accordance with claim 7 wherein the weight-halving temperature of the comb-like polymethacrylate based viscosity index improver is at least 320° C.
11. The lubricating oil composition in accordance with claim 7 wherein the sulphur content of the lubricating oil composition is at most 0.25 weight % in terms of the total weight of the lubricating oil composition.
12. The lubricating oil composition in accordance with claim 7 wherein a sulphated ash content of the lubricating oil composition is at most 0.6 weight % in terms of the total weight of the lubricating oil composition.