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Concentration of CO2 in the Atmosphere


• Excessive idling can actually damage your engine components, including cylinders, spark plugs and exhaust systems. Fuel is only partially combusted when idling as an engine does not operate at peak temperature. This causes fuel residue to build up on cylinder walls that can damage engine components and increase fuel consumption. (from the California Energy Commission).

• There are more than 557,000 Vermont Car and Truck registrations (as of end of 2010). If many Vermont vehicles reduced their idling by five minutes/day, the total CO2 emissions reduction could exceed 50,000 tons/year. (based on calculation from Office of Energy Efficiency – Natural Resources Canada).

Break the idling habit and we all breathe easier.

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  • Eric

    While I agree with not idling for the most part, it always drives me crazy to see the incorrect claims about idling damaging the engine. While certainly not ideal, if warm idling was so bad we wouldn’t see police cars and taxis with 300K+ miles on them, and note those miles don’t count the idling time.

    Modern fuel injected engines which are properly tuned always run in a closed loop once they are warm and with a computerized ECU controlling the fuel flow you will not use a single drop more fuel than the engine needs whether idling or not. The main effect of excessive idle is that you may need to perform maintenance “sooner”, including oil changes, since you would be running the engine without racking up miles on the odometer which is usually what scheduled maintenance is based on, but that does not mean it is “bad” for the engine.

    Not polluting and not wasting money/gas are reason enough, I don’t now why there is the need to repeat these false claims everywhere.

    Also, in extreme cold (i.e. sub zero) temperatures, even with a block heater, it can be hazardous to drive immediately without letting hoses and pumps warm up. Many early 2000’s BMW V8 engines for example have poorly designed positive crankcase ventilation systems which can freeze in extreme cold leading to excessive crank case pressure which can force the engine oil past the seals at an alarming rate. It isn’t enabled immediately though, it only kicks in once it enters closed loop. If you let the car idle and warm up slowly, this gives the intake manifold and PCV hoses time to warm up, but if you drive right away the engine may enter closed loop before the PCV system is warm and then you can end up with a catastrophic oil leak and possibly engine failure, not to mention the fire hazard from so much oil spewing down on hot exhaust headers, etc. I’ve known many BMW owners who had more than one warranty claim because of this issue.

  • Any use of the engine will shorten its life expectancy. While it is unavoidable for the engine to run when transporting occupants and to idle in traffic, increased engine wear associated with stationary warm-up idling can and should be avoided. I will list seven sources that confirm that idling not only requires more frequent engine maintenance, but does damage the engine, as described in the Tip. Before I do so, it is true, that in sub-zero temperatures it is necessary to warm-up the engine for one to three minutes (up to 10 minutes for heavy-duty diesels). This is stated on the Idle-Free VT website. Otherwise, while there are a few exceptions for older and poorly maintained vehicles, driving slowly to moderately is the best, most efficient way to warm up, allowing wheel bearings, steering, suspension, transmission and tires to warm up. Re police cars and taxis with 300K+: it is almost certain the engines of these vehicles have had more frequent than normal oil changes and maintenance, and I would suspect in many cases have had engine rebuilds.

    Now, I’ll let the experts speak…

    1. Callifornia Energy Commission: Consumer Energy Center
    Myth #2: Idling is good for your engine. Reality: Excessive idling can actually damage your engine components, including cylinders, spark plugs, and exhaust systems. Fuel is only partially combusted when idling because an engine does not operate at its peak temperature. This leads to the build up of fuel residues on cylinder walls that can damage engine components and increase fuel consumption.

    2. EPA New England: “What you should know about truck engine idling”
    Idling Causes Excessive Engine Wear
    • Running an engine at low speed (idling) causes twice the wear on internal parts compared to driving at regular speeds. According to the American Trucking Association, such wear can increase maintenance costs by almost $2,000 per year and shorten the life of the engine.

    3. 2010 Chrysler PT Cruiser owner’s manual (pg. 282)
    Change Engine Oil
    Road conditions and your kind of driving affects the interval at which your oil should be changed. Check the following list to decide if any apply to you.
    • Day and night temperatures are below 32°F (0°C).
    • Stop and go driving.
    • Extensive engine idling.
    • Driving in dusty conditions.
    • Short trips of less than 10 miles (16 km).
    • More than 50% of your driving is at sustained high
    speeds during hot weather, above 90°F (32°C).
    • Trailer towing.
    • Taxi, Police, or delivery service (commercial service).
    • Off-road or desert operation.

    4. 2009 Dodge Ram Diesel owner’s manual (pg. 47)
    Engine Idling
    Avoid prolonged idling. Long periods of idling may be harmful to your engine because combustion chamber temperatures can drop so low that the fuel may not burn completely. Incomplete combustion allows carbon and varnish to form on piston rings, engine valves, and injector nozzles. Also, the unburned fuel can enter the crankcase, diluting the oil and causing rapid wear to the engine.

    5. EPA Clean School Bus
    Engine Wear-and-Tear
    School bus engines do not need to idle more than a few minutes to warm up. In fact, extended idling causes engine damage. Engine manufacturers generally recommend no more than three to five minutes of idling.
    • Caterpillar Inc. cautions drivers to “… Avoid excess idling. If the vehicle is parked for more than five minutes, stop the engine. Excessive idling can cause carbon buildup and/or excessive idling can cause the engine to slobber. This is harmful to the engine.”
    • IC Corporation’s engine manual states that “…Excessive idling reduces fuel economy, and may decrease oil life.”
    • Cummins Inc. suggests idling for only three to five minutes before operating with a load.

    6. For Construction Crack Down on Idle Time
    • Mike Powers, product development manager for Caterpillar Global On-Highway, agrees, noting, “There is no additional wear when shutting the truck on/off several times a day. There are benefits in fuel economy and wear/durability when shutting the truck down rather than idling.”
    • “Starting and stopping the engine is actually easier on the engine than prolonged idling,” says Brian Lindgren, vocational sales director, Kenworth Truck Co.

    7. Natural Resources Canada – FleetSmart: Idling Gets You Nowhere
    What Happens When You Let an Engine Idle?
    • Increased Maintenance Expenses
    When a gasoline or diesel engine idles for prolonged periods, the engine oil becomes contaminated more quickly than when the vehicle is being driven. Oil contamination is more prevalent in diesel engines because of the large amount of intake air used in the diesel combustion cycle. When idling at low revolutions per minute (rpm), such as 600 rpm, the excess air in the combustion process cools the cylinder liners, resulting in incomplete combustion and condensation of unburned fuel on the cylinder walls. These deposits are eventually drawn into the engine sump where they contaminate the engine oil and reduce its effectiveness as a lubricant.
    Controlled studies demonstrate that prolonged idling typically reduces the operating life of engine oil by 75 percent, from 600 engine-hours to 150 engine-hours.
    • Shorter Periods Between Engine Rebuilds
    Idling produces carbon deposits and unburned fuel residues that will accumulate and damage the engine at several vital points. If you idle your truck excessively, you can expect to pay for more frequent servicing of spark plugs, fuel injectors, valve seats and piston crowns.

  • Eric

    As I said before, I agree with not idling, but nothing you or the “experts” mention actually show that idling is any worse than using your engine at all. There is no doubt that it results in more maintenance… though full engine rebuilds should be rare if you perform proper oil changes and other maintenance properly. I know a few people who own those same problematic BMW V8 engines I mentioned who have 500k+ miles without any rebuild, only regular maintenance. Idling itself is not going to “damage” the engine. Failing to perform the appropriate maintenance is what “damages” engines.

    I cannot stress enough that I totally support not idling, it is wasteful and unnecessary in most (but not quite all) circumstances. I just wish people would stick to the facts instead of repeating vague claims of mechanical engine damage without understanding what they are talking about.

  • mataliandy

    During idling the engine does not work at its most efficient mode, and the fuel combustion is incomplete. That leads to glazing of combustion chamber and reducing effectiveness of spark plugs in petrol engines (plugs with heavy deposits can foul, and that can reduce fuel consumption by 4 to 5%). Also petrol can contaminate the motor oil which reduces its lubricating qualities (that could mean more frequent oil changes and/or increased wear on the engine).

    Also, as the engine runs at less than ideal operating temperature, which causes water vapour (a product of combustion) to accumulate in exhaust system (at proper temperature and at higher speed of exiting gasses caused by increased RPMs it clears out pretty good), which leads to corrosion. Also, idling produces up to 10–12% more emissions than driving for the same amount of petrol used, due to incomplete combustion and ineffective operation of catalytic converter.

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