Novel thickeners for oil-containing compositions are crystalline polymers,
preferably side chain crystalline polymers, which (a) have a crystalline
melting point, T.sub.p, and an onset of melting temperature, T.sub.o,
such that T.sub.p-T.sub.o is less than T.sub.p.sup.0.7; (b) are soluble
in the oil at temperatures above T.sub.p, and (c) have been dispersed in
the oil by a process which comprises (i)dissolving the polymer in the oil
at a temperature above T.sub.p, and (ii) cooling the solution from step
(i) to crystallize the polymer in the oil.