Myth: Diesel engines need to warm up at idle for 5 to 10 minutes or more especially on cold days before driving them. Fact: This is one of the most common myths about diesel engines. Most engine manufacturers recommend that newer diesel engines idle for no more than 3 minutes before driving.
Unnecessary idling wastes fuel, causes air pollution and increases engine wear. An idling diesel engine produces much higher emissions than it would while using the same amount of fuel under load. Extended idling causes a build-up of soot inside the engine and results in a puff of black smoke when the engine revs.
It is true that diesel engines use barely any fuel while idling, far less than a gasoline engine. Diesels are durable engines anyway, and a semi driver who lets his engine idle overnight to keep warm can still expect to get hundreds of thousands of miles out of his engine.
Dan explained that three to five minutes is usually sufficient for cooling down a diesel engine. He also said it isn't necessary when just running about town without the trailer. But after long hauls you may want to idle the engine for up to seven minutes to allow the manifold to cool down.
Idling a heavy-duty truck consumes about 0.8 gallon of fuel per hour. Even when diesel costs as little as $2.50 a gallon, fuel for one 10-hour rest period will cost $20. Typically, a long-haul truck idles about 1,800 hours per year, using about 1,500 gallons of diesel.
Unlike gasoline engines which run at a constant air to fuel ratio of 14:1, diesel engines use a variable fuel ratio. At idle they may be as low as 200:1 while under heavy load it may be 5:1. So diesel engines at idle consume very little fuel leaving little reason to shut them off.
Idling your car for 30 seconds to a minute is acceptable, and it will not cause any harm to your vehicle. With advanced technology, even if you let your car idle for a slight longer duration, it will not damage it.
As a general rule of thumb, if it is below zero degrees Fahrenheit, you should allow your engine up to seven minutes to warm up. If the temperature is between zero and fifty degrees, the warm-up period should be three to five minutes. Over fifty degrees will only require one or two minutes to warm up.
In a vacuum (and with infinite fuel), your engine would continue to run forever. But in reality, several things might occur if your car idles for too long. To avoid running your car for too long, you should only idle your vehicle for a few minutes at most before either moving your vehicle or turning the engine off.
Letting a vehicle idle does more damage to the engine than starting and stopping. In fact, running an engine at low speed (idling) causes twice the wear on internal parts compared to driving at regular speeds1. Excessive idling can also cause a buildup of carbon residue in a truck's engine.
Idling longer than 10 seconds uses more fuel and produces more CO 2 compared to restarting the engine.
Short trips do not let the diesel engine get warmed up well enough to remove deposits and keep carbon from accumulating and being burnt off. That's all really. You need at least 15-20 minutes of loaded running to get it to temp and say about 1 hour straight a month of highway driving minimum to keep it all happy.
There is more concern over long periods of idling of heavy-duty diesel engines while the vehicle is parked and not in active service. This may have more of an adverse environmental impact and be a source of significant additional—and often unnecessary—fuel consumption.
Modern diesel vehicles have better cooling systems than those of old and are designed to warm-up the vehicle quickly. Letting the vehicle start and idle for a minute or two will not hurt it and will only help but much more than that is really unnecessary in my opinion.
How long do they idle? Do you track the engine hours? Did you know: On average, one hour of idle time is equal to 30 miles of driving.
Truckers, both independent owner-operators and fleet drivers, leave their engines idling for three main reasons: weather conditions, economic pressures, and old habits. In cold weather, a truck's engine and fuel tank need to stay warm.
Need to be driven daily, else maintenance becomes high
This is by far the most common misconception. Modern diesel cars do not need constant attention. You can use it when you need to. Else you can park it safely without worrying about the parts becoming jammed.
The damage begins with the liquids evaporating, leaving behind a thick substance that clogs the engine's moving parts. Ultimately, these parts will stick and begin to deteriorate. If given enough time, the engine will rust and fail to start.
Diesel engines are built to finer tolerances than are gasoline engines. They will accept much more abuse and often deliver, if well maintained, 8,000 hours of hard work before need a major overhaul.
You're not Letting Your Engine Warm Up
Let your engine warm up like you warm up in the morning. Let the glow plugs and intake heater do their job. Fire the engine and give it some time for the combustion heat to warm the engine evenly. This practice is very important on extremely cold mornings.
Driving a diesel engine hard will produce less soot per kWh of useful work. Period. Forget about the momentary puff of black smoke you sometimes see as the turbo spools up. It is the net effect that matters.
The diesel fuel in your fuel tank will become like gel at a temperature of 15ºF or -9.5ºC and you will have trouble starting your engine. Anything below 15ºF / -9.5ºC can and will cause problems for your diesel vehicle.
When it comes to the modern vehicle sitting in your garage today, you shouldn't let your engine idle. Your vehicle does not need more than a few seconds to start up. Leaving it idling actually can be detrimental, and it wastes fuel, which causes a negative environmental impact as well.