Abstract: 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.