Flushing is designed to rid the engine of any residue and debris that clogs up the mechanisms and hinders their performance. To flush the engine, the oil is removed and a chemical is poured in where the oil would normally go so that it flows through various parts of the engine, removing any gunk along the way. After the chemical has done its job and flowed back out of the engine through the bottom, new oil is added. Though this type of treatment is seldom needed on newer cars, old cars where the old hasn’t been changed in a long time may benefit from flushing the engine. Other systems requiring flush services include, radiator and cooling systems, power steering, transmissions, differentials and brake systems. All of these systems lubricate components that can be equitably as expensive as engines.