Lubricating oil composition for four stroke engine

Abstract

The lubricating oil composition for four-stroke cycle engine of the present invention includes a base oil (A) and from 0.5 to 10% by mass of a polyolefin (B) having at least an isobutene-derived constituting unit and having a number average molecular weight of 500 to 10,000, with a sulfated ash content being from 0.3 to 1.2% by mass.

1 . A lubricating oil composition for four-stroke cycle engine, comprising a base oil (A) and from 0.5 to 10% by mass of a polyolefin (B) having at least an isobutene-derived constituting unit and having a number average molecular weight of 500 to 10,000, with a sulfated ash content being from 0.3 to 1.2% by mass. 
     
     
         2 . The lubricating oil composition for four-stroke cycle engine according to  claim 1 , wherein the sulfated ash content is from 0.3 to 0.7% by mass. 
     
     
         3 . The lubricating oil composition for four-stroke cycle engine according to  claim 2 , further comprising an overbased calcium salicylate (C1) having a base number of 170 to 400 mgKOH/g and a neutral metal-based detergent (C2) selected from a neutral calcium sulfonate having a base number of 50 mgKOH/g or less and a neutral calcium salicylate having a base number of 50 mgKOH/g or less; and having a calcium content of 500 to 1,800 ppm by mass. 
     
     
         4 . The lubricating oil composition for four-stroke cycle engine according to  claim 2 , further comprising a hindered phenol compound (F1) and an alkyldiphenylamine compound (F2), with a sum total of the contents thereof being more than 1.5% by mass and 5.0% by mass or less on the basis of a total amount of the composition. 
     
     
         5 . The lubricating oil composition for four-stroke cycle engine according to  claim 2 , which is adapted to function as a lubricating oil composition for a four-stroke cycle engine in which a maximum power is 200 kW or more, an operation at 60% or more of the maximum power is continued for 10 hours or more, and an oil replacement cycle is 500 hours or more. 
     
     
         6 . The lubricating oil composition for four-stroke cycle engine according to  claim 1 , wherein the sulfated ash content is more than 0.7% by mass and 1.2% by mass or less. 
     
     
         7 . The lubricating oil composition for four-stroke cycle engine according to  claim 6 , further comprising an overbased calcium salicylate (C1) having a base number of 170 to 400 mgKOH/g and a neutral metal-based detergent (C2) selected from a neutral calcium sulfonate having a base number of 50 mgKOH/g or less and a neutral calcium salicylate having a base number of 50 mgKOH/g or less; and having a calcium content of more than 1,800 ppm by mass and 3,500 ppm by mass or less. 
     
     
         8 . The lubricating oil composition for four-stroke cycle engine according to  claim 6 , further comprising a hindered phenol compound (F1) and an alkyldiphenylamine compound (F2), with a sum total of the contents thereof being more than 1.5% by mass and 6.0% by mass or less on the basis of a total amount of the composition. 
     
     
         9 . The lubricating oil composition for four-stroke cycle engine according to  claim 6 , which is adapted to function as a lubricating oil composition for a four-stroke cycle engine in which a maximum power is 200 kW or more, an operation at 60% or more of the maximum power is continued for 10 hours or more, and an oil replacement cycle is 1,000 hours or more. 
     
     
         10 . The lubricating oil composition for four-stroke cycle engine according to  claim 1 , wherein the polyolefin (B) is a polybutene. 
     
     
         11 . The lubricating oil composition for four-stroke cycle engine according to  claim 10 , wherein the polybutene is polyisobutene. 
     
     
         12 . The lubricating oil composition for four-stroke cycle engine according to  claim 10 , wherein the polybutene is non-hydrogenated. 
     
     
         13 . The lubricating oil composition for four-stroke cycle engine according to  claim 1 , further comprising a polybutenyl succinic acid imide (D1) and a boron-modified polybutenyl succinic acid imide (D2). 
     
     
         14 . The lubricating oil composition for four-stroke cycle engine according to  claim 1 , further comprising a zinc dithiophosphate (E) in an amount of 100 to 1,000 ppm by mass as expressed in terms of a phosphorus atom on the basis of a total amount of the lubricating oil composition. 
     
     
         15 . The lubricating oil composition for four-stroke cycle engine according to  claim 1 , which has a kinematic viscosity at 100° C. of 6.9 mm 2 /s or more and less than 21.9 mm 2 /s. 
     
     
         16 . The lubricating oil composition for four-stroke cycle engine according to  claim 1 , which is adapted to function as a lubricating oil composition for a gas cogeneration system. 
     
     
         17 . A lubricating method, comprising performing lubrication between respective parts in a four-stroke cycle engine with the lubricating oil composition for four-stroke cycle engine according to  claim 1 . 
     
     
         18 . A method for producing a lubricating oil composition for four-stroke cycle engine, the method comprising:
 blending a base oil (A) with from 0.5 to 10% by mass of a polyolefin (B) based on the total amount of the lubricating oil composition, the polyolefin (B) having at least an isobutene-derived constituting unit and having a number average molecular weight of 500 to 10,000; and   regulating a sulfated ash content to from 0.3 to 1.2% by mass.   
     
     
         19 . The production method of a lubricating oil composition for four-stroke cycle engine according to  claim 18 , wherein the sulfated ash content is from 0.3 to 0.7% by mass. 
     
     
         20 . The production method of a lubricating oil composition for four-stroke cycle engine according to  claim 18 , wherein the sulfated ash content is more than 0.7% by mass and 1.2% by mass or less.