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Preheat Your Diesel Engine for Fuel Savings, Improved Performance, Reduced Costs

Posted by Cummins Expert on

Cold starts and idling increase emissions, reduce efficiency and cost you money.

Why should you pre-heat your diesel engine, even if it’s 35°C outside? Isn’t that warm enough? The short answer is no. Engines want to run at high temperatures to reduce emissions and run efficiently. 

Put simply, cold engines smoke and warm engines don’t.

Most diesel engines want to operate at roughly 65-70°C. So, even if it’s a hot day at the equator, the engine will still be considered “cold” if it’s not up to its ideal temperature. A smoking engine means higher particulate matter, which in turn means more soot and particulate deposits on your diesel particulate filter (DPF). And because a cold engine start emits un-combusted fuel, the soot and particulate matter are wetter and heavier and can overload the DPF, reducing engine efficiency and leading to more frequent filter cleanings.

More soot and particulate matter, especially denser emissions, can result in filter overloading, face plugging and thermal cracking. Any one of these can lead to reduced engine and fuel efficiency, more frequent DPF cleanings, and ultimately, more money spent on repairs and maintenance.

Idling is not the answer.

Excessive engine idling, even if you think it’s ‘warming’ the engine, isn’t an ideal scenario either. Similar to cold starts, engine idling doesn’t actually raise the exhaust gases to a high enough temperature for the DPF to perform a regeneration. DPF regenerations occur to help burn harmful PM and NOx gases into ash so they aren’t emitted as exhaust.

Plus, idling the main power unit uses a lot of fuel. An idling Class 8 diesel is estimated to use more than 1 litre of fuel every hour of idling. A Webasto Thermo Top C can provide up to 10 hours of operation on a single litre. Typically, you will only run the Thermo Top C for approx. 30-60 min prior to starting the trucks engine.

Pre-heating the engine IS the answer.

Pre-heating the engine has many benefits, including reduced engine wear and tear, fuel savings, improved fuel efficiency and lower emissions. Heaters come in two options, electric block heaters and fuel-fired coolant heaters.

Electric block heaters only heat one area of the engine and coolant, and they do not circulate to heat all of the coolant. This is less efficient, uses more power and takes more time.

Fuel operated coolant heaters, on the other hand, integrate with the engine’s own coolant system and circulate warmed coolant throughout, thus warming from the inside out in a process called pre-conditioning the engine. This method is much more efficient and has beneficial side effects, such as warming the engine oil (which decreases pressure on gaskets and seals at startup). Warm fuel injectors and EGR valves are much less likely to be soiled by carbon buildup blowing through the exhaust system. There’s also a side benefit for the driver: leaving the cab vents open warms the cab area. It’s a win all the way around. 

The goal of a coolant heater is to warm the engine before starting the power unit. The biggest benefit of this process is fuel savings. By not idling the vehicle, you’re saving money. Want to calculate how much? Check out our Webasto coolant heater ROI calculator to see how the return on investment plays out in as little as six months, just on fuel savings. Add to that the savings on engine and DPF maintenance, and that timeline to savings is even shorter.

The biggest reward? Less downtime and reduced maintenance costs.

The benefits of pre-heating your diesel engine the right way multiply over time, in that you’ll see reduced engine downtime, which translates nicely into less money spent on repairs and maintenance. Coolant heaters like the Webasto Thermo Top C use as little as 3.7 litres of fuel in 10 hours and reduce particulate matter emissions by as much at 66% at start-up. Operation is quiet, so drivers won’t be disturbed while resting, and they’re CARB approved and EPA SmartWay verified. 

Save fuel and money, reduce emissions and downtime, and extend the life of your DPFs and engine. If you’re looking at pros and cons, it’s a no-brainer.

Check out Cummins’ full line of Webasto coolant heaters.


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