Idle Time, Does It Harm My Diesel Engine?

Idle Time

Does idling your diesel powered vehicle have long term effects on the engine? One would think not, since diesels have been around for years, and idling on big rigs has always been the norm for over-the-road truckers.

The diesel engines of years past have changed drastically to keep up with emission standards and computer controlled engines. Since 2007, the diesel engine has seen a change in the way the engines exhaust is measured and purified.

Components were added to help reduce the carbon the engine emits helping to keep our air cleaner. But is it all really working and at what cost?

Changes In 2007

The 2007 standards include a 50% reduction in the various nitrogen oxides (NOx) produced during combustion and a 90% reduction in particulate matter emissions compared to 2004 standards. The regulation requires on-vehicle monitoring of the performance of the engine’s emissions system.

The industry standard is called Engine Manufacturer Diagnostics (EMD) and will detect issues within the emissions control system and inform the driver with indicator lights on the dashboard.

Since engine changes alone cannot meet the new requirements, new “clean diesel” technologies include improved electronic control systems, ultra-low sulfur diesel (ULSD), exhaust after treatment such as catalytic converters and diesel particulate filters (DPF), enhanced exhaust gas recirculation (EGR), cooling system changes (due to higher heat loading), and fuel/air ratio change


A diesel particulate filter, or DPF, is an exhaust after treatment device that traps particulate matter such as soot and ash. A DPF typically uses a substrate made of a ceramic material that is formed into a honeycomb structure. 

In order to reduce emissions from diesel vehicles, diesel particulate filters capture and store exhaust soot, which must be periodically burned off to regenerate the filter. The regeneration process burns off excess soot deposited in the filter, which prevents harmful exhaust emission and the black smoke you commonly see emitted from diesel vehicles when accelerating.

The life of the DPF is substantially reduced if non-ULSD is used. Typically, DPFs need to be cleaned of noncombustible materials (“ash” that comes from the unburned detergents from engine oil) every 150,000 to 200,000 miles using an exchange program or “clean it on the truck” process estimated to cost between $150 and $400.

Equating Hours To Miles

So what does this have to do with idling? Hours of idling adds miles to your engine. First you need to determine how many hours have accumulated on your engine. Multiply the amount of hours on your engine by 60.

Use the number you come up with to estimate how many miles is on your engine. For example, 1,235 hours on an engine equates to approximately 74,100 miles. Just knowing how many more miles you have racked up on the engine isn’t the only thing to worry about. If you change your oil every 6,000 miles, divide 74,100 by 6,000, leaving you with 12.35 missed oil changes, fuel filters, which will eventually lead to early engine failure.

Over the course of a year, a long-haul truck will idle about 1,800 hours, using nearly 1,500 gallons of diesel. For one heavy truck, the cost of idle fuel waste averages about $4,000. The cost of poor fuel efficiency for a large fleet of vehicles is high. This equates to 1.2 gallons of fuel per hour.

If you plan on purchasing a diesel powered vehicle, understand the maintenance these engines require today, otherwise you might be racking up expensive repair bills. Happy Motoring

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