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Indiana Department of Environmental Management

Indiana Department of Environmental Management

Pollution Prevention > Voluntary Idling Program > Diesel Idling Facts and Myths Diesel Idling Facts and Myths

  • Myth: Diesel engines need to idle for 5 minutes or more in the morning, especially on cold days.
    • Fact: This is one of the most commonly held myths in North America concerning diesel engines. Most engine manufacturers recommend that newer diesel engines run for no more than 3 minutes before driving.
    • Gelling of diesel fuel used to be a problem, but refiners have worked to resolve this issue by creating winter blends that better withstand colder temperatures.
    • Letting an engine idle actually does more damage to the engine than starting and stopping. Running an engine at low speed (idling) causes twice the wear on internal parts compared to driving at regular highway speeds, which can increase maintenance costs and shorten the life of the engine.
    • Please check your owner's manual to find out specific warm-up guidelines for your vehicle.
  • Myth: Idle reduction technologies are not cost effective.
    • Fact: Idle reduction technologies that save fuel or use fuel more efficiently can pay for themselves through fuel savings. The initial cost and fuel savings dollars can be used to determine the payoff point on these fuel savings technologies. From that point on, all fuel savings are pure profit.
    • Recent financial reports demonstrate that retrofits can drastically reduce idling fuel consumption in long-haul fleets and can pay for themselves in less than two years.
  • Myth: Diesel exhaust doesn't hurt anyone.
    • Fact: Diesel exhaust contains several chemicals and compounds that may be detrimental to human health. The health effects of diesel exhaust are both acute, from short-term exposure, and chronic, from long-term or repeated exposure. Specific health risks and their severity depend upon the amount of chemical that you are exposed to as well as the duration of the exposure.
    • An acute exposure to diesel exhaust could cause an irritation of the eyes, nose, throat, and lungs as well as lightheadedness. Chronic exposure to diesel exhaust can have several more severe effects on human health. Chronic exposure is likely to occur when a person works in a field where diesel fuel is used regularly or has repeated exposure to diesel fumes over a long period of time. Human health studies demonstrate a correlation between exposure to diesel exhaust and increased lung cancer rates in occupational settings. Experimental animal inhalation studies of chronic exposure to diesel exhaust have shown that a range of doses cause varying levels of inflammation and cellular changes in the lungs. Human and laboratory studies have also provided considerable evidence that diesel exhaust is a likely carcinogen.
    • Please visit the IDEM DieselWise Health Effects Page for more information about the health effects of diesel exhaust.
  • Myth: Heavy-duty diesel truck idling does not waste that much fuel.
    • Fact: Fuel is a large expense for the trucking industry. Idling adversely impacts fleet and truck owners by increasing both fuel and maintenance operating expenses. An hour of idling time consumes about one gallon of diesel fuel.
    • It is estimated that idle reduction technologies could reduce fuel usage by an additional 1 billion gallons annually. This translates into over $3 billion additional dollars that could be saved by reducing fuel cost.

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