A Few Facts About Idling You can help clean up the air. Just turn off your engine and don't idle. Idling gets you nowhere - and it can be costly. Excessive idling wastes an enormous amount of fuel and money and generates needless air pollution and greenhouse gases. Here are a few things you might not know about idling ... Idling emits more pollution if the catalytic converter is not working properly. Ask your technician to check the system the next time your car is being serviced. Learn more from Otto Parts! Diesel exhaust contains microscopic soot, a particle that is about 200 times smaller than the period at the end of this sentence. Diesel exhaust contains both very small particles and 40 chemicals that are classified as "hazardous air pollutants" under the Clean Air Act. In most cases, it is more efficient to turn off most warmed-up vehicles than to idle for more than 30 seconds. Excessive idling can be hard on your engine. Because an engine is not working at its peak operating temperature, fuel does not undergo complete combustion. This leaves fuel residue that can contaminate engine oil and makes spark plugs dirty.