Engine Flush
A chemical additive added to old engine oil before an oil change to dissolve sludge, deposits, and varnish from internal passages.
An engine flush is a chemical solvent treatment designed to clean the internal oil channels and passages of an engine. Over time, engine oil can break down and combine with fuel soot, carbon, and moisture to form a thick black sludge that blocks oil passages and restricts lubrication flow to critical bearings.
To perform a flush, the chemical additive is poured into the oil filler neck with the engine warm. The engine is then allowed to idle for a set period (typically 10 to 15 minutes) without driving. The solvents circulate through the engine, dissolving carbon deposits and suspending the sludge in the oil. The oil is then immediately drained, and a new filter and fresh oil are installed.
While beneficial for neglected engines, flushes should be used with caution. In high-mileage engines with heavy buildup, a flush can loosen large chunks of sludge that can clog the oil pump pickup screen, starving the engine of oil. Regular oil changes remain the best preventative maintenance against sludge.