Engine flushing is a procedure that is used to clean the engine of sludge and other elements that build up in various parts of the machinery over time. The main purpose of this procedure is to prolong the life of the engine. By flushing an engine periodically, the internal components of the engine remain relatively clean and thus perform at optimum levels.
The process employed to flush an engine is somewhat similar to transmission flushing. With a transmission flush, the usual flow of fluid through the mechanism is used to push old fluid and various contaminants out of the system via the drain plug. With an engine flush, the cleansing chemicals are introduced and allowed to circulate through the engine, following the same flow pattern as the oil that lubricates the engine components. The chemicals eventually make their way to the oil pan, where the chemicals and the sludge they have removed deposit.
While in theory the engine flush seems like a task that should be performed from time to time, not everyone agrees that the flush is effective. While it is generally acknowledged that this process is helpful in low mileage vehicles that have not had the oil changed as often as recommended, some professional mechanics question the effectiveness of the flush with high mileage vehicles. The idea is that the buildup of sludge and deposits in the older engine may be more than the chemicals in the flush can process, resulting in making a bad situation worse. Instead of using an engine flush, they recommend that the engine be dismantled and the components thoroughly cleaned, assuming the engine is still in working order.
Because of the difference of opinion among professionals regarding the effectiveness of an engine flush, not every garage or automotive center will offer this service. Even among the mechanics who do offer engine flushes will generally evaluate the condition of the engine before recommending the procedure.
It is important to note that an engine flush is not a substitute for using the proper weight and grade of oil, or having the oil changed according to manufacturer recommendations. At best, it should be considered a way to augment proper maintenance and thus help to prolong the life of the engine.