Conventional gasoline-fueled vehicles are not very efficient. Approximately 15% of money spent on fuel is used for propulsion (movement) or running accessories, like the A/C. Inefficiency in the internal combustion engine causes unburned deposits to build up in the engine. Dirty air may also come in through the air filter during the intake process. While the engine oil is lubricating all the critical engine components, it also cleans by removing particles of carbon and other contaminants. As the oil is pumped throughout the engine, the dirty particles are screened out by the oil filter. Clean engine components help ensure proper lubrication.