Abstract: Impurities dissolved in a solid polymer and/or trapped in the spacial volume of the polymer can be removed quickly and efficiently in one or more relatively short pressurization/depressurization cycles, using a penetrant fluid (e.g. carbon dioxide) having at least some solubility in the polymer. Polymers with inherently slow or delayed elastic recovery at the temperature or temperatures at which the cycle is carried out (e.g. within the range of 20 to 200.degree. C.) or polymers with a high T.sub.g are the ones most efficiently treated. The penetrant is used to expand the polymer matrix, increasing its spacial volume. The pressure is then decreased rapidly, so that the impurities will migrate out of the polymer matrix before the matrix has a chance to relax or return to substantially its original volume. Each complete cycle should last seconds or minutes rather than hours.

Abstract: Deposit formation can be reduced and primary oxidation of the lubricant can be retarded in a lubricant when used in an internal combustion engine by incorporation of soluble copper (e.g., 1,500 to 3,000 ppm) in the lubricant.