Ask Joe Mechanic - Engine Flushing

A hotly debated subject is engine flushing and whether it is beneficial or it is actually harmful to an engine. No two technicians seem to agree as to whether you should perform this service on your vehicle.    

The process of engine flushing is used to clean sludge, dirt and deposits that build up in the internal parts of an engine, especially inside the valve cover and the oil pan over time. The main purpose of performing an engine flush is to try to extend the life of the engine. By flushing an engine periodically, the inside of the engine will hopefully stay relatively clean and will operate more efficiently. 

The method used to flush an engine is somewhat like what is used to flush a transmission. When flushing a transmission, the fluid is pushed through the transmission to carry the old fluid and dirt and deposits out of the transmission by way of the drain plug. With engine flushing, a cleaning chemical is added to the engine oil and circulates through the lubrication system. The chemicals eat away at the deposits, eventually making their way into the oil pan, where they collect in the bottom of the pan to allow it to be drained.

While the theory behind flushing an engine seems like something that should be done on a periodic basis, there is much disagreement as to whether it is smart and effective to do. While it is general knowledge that it can be beneficial in low mileage vehicles that have not had proper maintenance performed, something that is often found to happen in lease vehicles where the leasee feels that it is not my vehicle and I am giving it back in two or three years, so why worry about changing oil and spending that extra money. Many technicians question whether it is a good idea in higher mileage vehicles. There is the chance in an older engine that the buildup of sludge may be more than the chemicals in the flush can properly loosen and remove, which could worsen a bad situation. Another fear is that the sludge will lie in the pan and clog the oil pump pickup screen and cause oil starvation. Instead of performing an engine flush, it is much more effective to disassemble and clean the engine as long as it is in good operating condition, even though this is more expensive, or else do a complete engine rebuild if it is determined that the engine is not in good condition. 

Because there is such a difference of opinion whether to do an engine flush or not, not every garage offers or recommends this service. Some facilities that used to do engine flushes, including a dealer where I used to work, no longer do so. Even in shops that do engine flushes, they will generally have a technician check the condition of the engine before they will do the flush. 

It is important to remember that there is no substitute for proper maintenance. If anything, an engine flush should be considered as a way to supplement the proper care of the engine and thereby help to prolong its life. Also, if you do choose to perform this service, I recommend having a professional do it and seek their advice first, I do not consider this a wise do it yourself procedure.