| abstract |
The invention provides a method of lubricating a compression-ignition internal combustion engine with a maximum laden mass over 2,700 kg comprising supplying to the engine a lubricating composition comprising: an oil of lubricating viscosity, 1.5 wt % to 10 wt % of an ashless dispersant, a 300 TBN or higher alkaline earth metal sulphonate detergent having a metal ratio of 10 to 40, and a 80 TBN or lower alkaline earth metal sulphonate detergent having a metal ratio of 1 to 5, wherein the lubricating composition comprises 0 wt % to 0.2 wt % of a phenolic based detergent, the ratio of higher alkaline earth metal sulphonate detergent to lower alkaline earth metal sulphonate detergent is 80:20 to 20:80, the total amount of soap delivered by the calcium sulphonate detergents is 0.4 wt % to 1.5 wt % of the lubricating composition, and the lubricating composition has a sulphated ash content of not more than 1.5 wt %. |