A composition containing metal based nanoparticles (X), a polymer (Y), and a dispersion medium, the polymer (Y) being a vinyl polymer having a chain-like alkyl group having 10 to 28 carbon atoms and a nitrogen-containing heterocyclic group, the metal based nanoparticles (X) and the polymer (Y) being dispersed in the dispersion medium, the composition being used as an additive composition for a lubricating oil composition, an additive composition for a grease composition, a lubricating oil composition, or a grease composition.

The polymer (Y) is one or more kind selected from the group consisting of a polymer (Y1) that contains two or more kinds selected from the group consisting of a constitutional unit derived from the following monomer (ya), a constitutional unit derived from the following monomer (yb), and a constitutional unit derived from the following monomer (yc), and a polymer (Y2) that contains a constitutional unit derived from the following monomer (yb) and does not contain a constitutional unit derived from the following monomer (ya) and a constitutional unit derived from the following monomer (yc): monomer (ya): an olefin having 12 to 30 carbon atoms, monomer (yb): a vinyl monomer having a nitrogen-containing heterocyclic group, at least one hydrogen atom of which is substituted by a chain-like alkyl group having 12 to 30 carbon atoms, and monomer (yc): a vinyl monomer having a nitrogen-containing heterocyclic group, all hydrogen atoms of which are not substituted by a chain-like alkyl group having 12 to 30 carbon atoms.

The present disclosure relates to microencapsulated friction modifiers additives used in lubricants or other solutions, to their preparation, and to the use thereof to improve fuel economy of the engines and machines by enhancing friction reduction and prolonging the friction reduction time period.