Oil consumption studies in a single-cylinder diesel engine using solid-film lubricants

Solid-film additives (tungsten disulfide, lead sulfide, and graphite fluoride) were dispersed in a high temperature liquid lubricant, and their performance was evaluated in a single-cylinder diesel engine. Oil consumption and wear of the piston and rings were determined during the tests, and changes in oil properties such as viscosity and total acid number (TAN) were monitored as well. Tungsten disulfide and lead sulfide proved to be effective additives to reduce friction and wear under the operational conditions encountered in the diesel engine. This contrasted with the behaviour of graphite fluoride, which produced high friction and wear. The observed oil consumption correlated with degradation rates of the solid-film additive dispersions as indicated by the TAN, although high abrasion was also observed in the case of graphite fluoride. The use of solid-film additives had no effect on the brake-specific fuel consumption with respect to the reference baseline oil.