Grease compositions

A lubricating grease, which is resistant to radiation from nuclear reactors, comprises (1) a mineral oil thickened to a grease consistency with carbon black and (2) more than 5% and up to 50% by weight, based on the total composition, of hydrocarbon polymer having a molecular weight up to 10,000. One or more hydrocarbon polymers may be employed, chosen for example from polyethylene, polypropylene, polyisobutylene and polystyrene. Hydrocarbon copolymers may also be present, for example butadiene/styrene copolymer or copolymers of a C4-C8 iso-olefin (e.g. isobutylene) with a small proportion of a C4-C6 conjugated diolefin (e.g. butadiene, dimethyl butadiene, piperylene or isoprene). The grease may also contain a minor proportion of an antioxidant, e.g. phenyl naphthylamine, N,N1-di-sec butyl-p-phenylene diamine, 2,4-dimethyl-6 - tert butyl - phenol, 2,6 - di - tert butyl-4-methyl-phenol, a bisphenol or phenothiazine. In the examples, mineral oil compositions are described containing acetylene black, phenyl-b -naphthylamine and polyethylene or polyisobutylene (with or without isobutylene/isoprene copolymer). The effect of omitting the hydrocarbon polymer is described.