In performing this function, the lubricant must remain relatively unchanged. Changes in thermal and oxidative stability will materially decrease a lubricant's efficiency in this regard. Additives are generally employed to solve such problems. The ability of a lubricant to remain effective in the presence of outside contaminants is quite important. Among these contaminants are water, acidic combustion products, and particulate matter.
Additives are generally the answer in minimizing the adverse effects of contaminants.