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A report from the AgTech Centre

Idling modern diesel engines costly for producers

Diesel engine idling increases fuel costs, causes premature engine damage, pollutes the environment and is largely unnecessary with today's modern engines, say engineers at Alberta Agriculture, Food and Rural Development's (AAFRD) AgTech Centre in Lethbridge.

"There are many ideas about the need for diesel idling that are based on outdated perceptions from years ago," says Reed Turner, an AgTech Centre Engineer. "Today's turbocharged diesel engines start a lot better and simply don't need to idle as much as many people think."

The costs of idling are often hidden but quickly add up to significant dollars, says Turner. Excessive idling is defined as running a diesel engine at 600 to 1,200 RPM, when the machinery itself is not in productive use. Research suggests heavy truck engines idle bewteen 25 and 45 percent of their total engine hours. Based on a farm fuel cost of $0.65 per litre, this adds up to $288 to $460 per 1,000 hours. Other costs are also incurred from excess engine use.

"The key fact for producers is these dollars represent a non-producing expense," he says. "An hour meter does not distinguish between revenue-generating production time and non-revenue generating idle time - both burn fuel and depreciate the engine value."

There are several common myths producers should be aware of to avoid needless costs, says Turner. Topping the list is the myth that diesel engines need to idle because they're hard starting. In fact, he says, today's diesel engines start easily when the engine operating systems are well maintained. "If an engine is hard starting, it's better to fix the problem than to let it idle."

Second is the idea that idling is necessary in cold weather to avoid a hard restart. "Modern engines exhibit good starting ability in all but the most extreme cold weather conditions," says Turner. "We also want producers to know that idling isn't the only option to help get an engine started or operating in cold weather. Block heaters are just one example of a cold starting aid for weather below -7° C, and oil heaters and fuel tank heaters can help if the engine is operated below -18° C."

Another common myth is that it's best to idle until the engine is fully warmed up. The reality is that it's impossible to bring a diesel engine to operating temperatures while idling, he says. Manufacturers recommend providing five to 10 minutes of fast idle time after a cold start, then lightly loading the engine until oil and coolant temperature have stabilized.

For cooling down after working an engine, the recommendation is to allow a period of fast idle, 800 to 1,000 RPM, says Turner. But this is only necessary until oil, coolant and exhaust temperatures have dropped and stabilized at the low end of their normal operating temperatures, typically about three to five minutes of idling time.

The belief that idling the engine is better than shutting it down is also a myth, says Turner. Idling is not within the manufacturer's predetermined RPM and load range for maximum performance and best fuel economy.

When idling unnecessarily, incomplete combustion occurs that causes over fueling. Under these conditions, combustion gases and fuel can enter the crankcase, cause deterioration to the oil additive package, and eventually cause premature engine damage, he says.

Some municipalities have enacted anti-idling bylaws, as a result of concerns about nuisance noise and emissions. A diesel engine, idling one hour per day for one year, produces about 2,700 kilograms of carbon dioxide and 45 kilograms of nitrogen oxides, says Turner.

The AgTech Centre, located in Lethbridge, Alta., is part of the Alberta Agriculture, Food and Rural Development Agricultural Engineering Branch. Its mandate includes all aspects of agricultural sustainability.

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