Abstract: An improved lubricating oil composition comprising a major amount by weight of oil of lubricating viscosity, a minor amount by weight of solid particles effective to improve the lubricating properties of the composition; and a minor amount of certain dispersant --VI improver materials. This composition provides improved inhibition of sludge and varnish formation in use.

Abstract: Improved internal combustion engine lubrication is obtained by the controlled rate of release of certain solid particles into circulating lubricating oil. Compositions are set forth comprising such solid particles combined with solid thermoplastic polymer having a controlled rate of dissolution in the lubricating oil. Also included are methods and apparatus wherein such solid particles are added to the engine lubricating oil, for example, which involve the filtering system for such oils.

Abstract: An improved lubricating oil composition comprising a major amount by weight of oil of lubricating viscosity; a minor amount by weight of solid particles effective to improve the lubricating properties of the composition; and a minor amount of a nitrogen containing mixed ester of a carboxy containing interpolymer. This composition provides improved inhibition of sludge and varnish formation in use.

Abstract: An improved lubricating oil composition comprising a major amount by weight of oil of lubricating viscosity; a minor amount by weight of solid particles effective to improve the lubricating properties of the composition; and a minor amount of an oxidized olefin polymer which has been reacted with an aliphatic amine or polyamine. Preferably, this reaction occurs in the presence of a formaldehyde-yielding reactant. This composition provides improved inhibition of sludge and varnish formation in use.

Abstract: An improved lubricating oil composition comprising a major amount by weight of oil of lubricating viscosity; a minor amount by weight of solid particles effective to improve the lubricating properties of the composition; and a minor amount by weight of at least one of certain specific polymers has been found to provide improved inhibition of sludge and varnish formation in use. The polymers useful in the present composition comprise(1) an olefin polymer, for example, an ethylene, propylene and 1,4-hexadiene terepolymer, with an dialkylaminoalkyl methacrylate grafted thereon;(2) an interpolymer prepared from a long chain n alkyl-methacrylate and a dialkylaminoalkylmethacrylate or a N (alkanone) acrylamide; or(3) mixtures thereof.

Abstract: An improved lubricating oil composition comprising a major amount of oil of lubricating viscosity; a minor amount by weight of solid particles effective to improve the lubricating properties of the composition; and a minor amount by weight of at least one of certain co-polymers derived from the polymerization of (1) an N-vinyl-pyrrolidone, and (2) an oil-soluble acrylic ester.An improved method for lubricating an internal combustion engine is also disclosed.