If your car's engine is low on oil, or if the oil is old and has accumulated debris, it can cause the oil passages to become blocked. This can lead to a loss of engine power and decreased fuel economy. To clear blocked oil passages, you will need to flush the engine with a solvent or petroleum-based cleaner.
Start by removing the oil fill cap and draining the oil into a catch pan. Next, remove the oil filter and discard it. With the filter removed, locate the oil pressure relief valve and unscrew it. Place a drain pan under the valve and open it to release the pressure. Once the pressure is released, remove the oil pan and drain the oil.
With the engine now empty of oil, you can begin flushing it with the solvent or cleaner. Pour the cleaner into the oil fill opening and let it run through the engine for several minutes. You may need to remove the spark plugs to ensure that the cleaner reaches all the oil passages. Once the cleaner has had a chance to work, replace the oil and filter and start the engine.