Method of operating an engine using an ashless consumable lubricant

A method of operating an internal combustion engine, wherein the internal combustion engine is equipped with a pilot ignition system, a lubricating system and a fuel system, comprising:

• (i) supplying to said engine's lubricating system a lubricant comprising:
• (a) an oil of lubricating viscosity;
• and
• (b) a succinimide dispersant with a TBN of at least 80 on a diluent-free basis, in an amount sufficient to provide at least 8 TBN to the lubricant;
• and
• (c) a combination of (i) an antiwear agent derived from a hydroxycarboxylic acid;
• (ii) a dispersant viscosity modifier comprising an amine-functionalised additive wherein the additive is derived from an amine having at least 3 aromatic groups, at least one —NH2 functional group, and at least 2 additional amino groups where the groups are secondary and/or tertiary amino groups;
• (iii) a dispersant viscosity modifier comprising the reaction product of:
• (a) a polymer comprising carboxylic acid functionality or a reactive equivalent thereof and (b) an amine component comprising at least one aromatic amine containing at least one amino group capable of condensing with said carboxylic acid functionality to provide a pendant group and at least one additional group comprising at least one nitrogen, oxygen, or sulfur atom;
• (iv) additives obtained from the reaction of:
• (1) an anthranilic anhydride;
• (2) a polymer containing an anhydride group, a carboxylic acid group, or an acyl group;
• and (3) at least one member selected from the group consisting of:
• an amine wherein the amine contains a primary or secondary amino-group, an alcohol, an aminoalcohol, and a thiol;
• wherein said lubricant has a zinc content of 0 to about 1000 ppm, a percent sulfated ash value of up to about 0.25, a phosphorus content of less than 50 ppm, and a sulfur content of up to about 0.4 percent by weight;
• (ii) obtaining a portion of the lubricant from the lubricating system;
• (iii) during the pilot ignition phase of the engine's combustion cycle or when a primary fuel is injected into the engine's combustion chambers from the fuel system, injecting the obtained lubricant portion into one or more of the combustion chambers or pre-combustion chambers of the engine in a ratio (by weight) of lubricant to primary fuel from about 0.1:100 to about 10:100.