Abstract: An adapter system for use with an internal combustion engine flushing apparatus which permits universal connection to the crank case and the lubrication system of a large number of different sizes and types of internal combustion engines. The adapter system comprises a first adapter referred to as a crank case adapter enabling a hose of a flushing apparatus to be connected within the drain plug port of an oil path of the engine. This first adapter is provided with a mechanism to enable the adapter to fit within the drain plug port of substantially all automotive vehicle internal combustion engines without being threadably secured within the drain plug hole. A second adapter set or so called lubrication system adapter set is comprised of a plurality of different lubrication system adapter pieces which individually or in combination fit at the oil filter port leading to the lubrication system of the internal combustion engine.