an electrically driven metering pump removes used oil in precise increments at a controllable rate of repetition from a safe operating level in the sump or reservoir of an engine , compressor , transmission or other power equipment ; preferably in combination with means provided by a circulating oil supply system , in which withdrawal of oil from the sump is at a controlled running level and oil for removal is taken from a withdrawal path in the supply system , using a separator to exclude air from the oil removed . oil removed by the metering pump is filtered and delivered to an electrically driven blending pump , which draws in engine fuel for combination with this oil by turbulence , repetitive transfer , heating and forced dispersion to produce a primary blend at a composition determined by the relative volumes of delivery per operating pulse and the relative rates of pulse repetition of the metering and blending pumps . the primary blend is then delivered to an engine fuel system , where it is mixed with more fuel to produce a final blend for disposal by burning in an engine . removal of used oil may be suspended or modified in rate in response to one or more operating variables , including demand , idling condition , speed , load , fuel consumption or level of fuel in a tank .