Diesel engines are known to be much more fuel-efficient than gas engines. They compress air at a much higher ratio and produce more energy per gallon of diesel fuel. Unfortunately, diesel engines don’t always perform well when the temperature drops. Cold weather can slow down the combustion process, which is why many vehicle owners recommend warming up your diesel engine before you start driving.
Note that most people don’t allow for a warm up unless the weather is really cold; they just let the glow plug “wait” light go out, fire it up, and drive away, because the engine will warm up anyway once it’s started. A diesel doesn’t typically warm up as quickly as a gasoline engine and it may take longer to get the coolant flowing through the heater core warm enough for cabin heat.
Preheating your engine is exactly what it sounds like. Before driving away, you warm up your engine for a few minutes. This typically involves activating built-in preheating systems in your vehicle, such as block heaters and coolant heaters.
If it’s cold, then yes, you should warm up your diesel engine before driving. Engine oil gets thicker when temperatures drop, which increases the viscosity of the oil (makes it thicker, like cold honey) until it warms up. Coolant and windshield washer fluid can also freeze after a particularly cold night.
Your diesel engine’s warm-up time will depend on several factors, such as your vehicle’s year, make, and model. One of the biggest factors to consider is how cold it is. It typically only takes 1 to 2 minutes for modern diesel engines to warm up when the temperature is over 50 degrees Fahrenheit. If the temperature drops to below zero degrees Fahrenheit, you’ll probably need to wait a bit longer.
It’s always best to follow your manufacturer’s recommended warm-up time, so you don’t end up preheating your engine for too long.
Warming up your diesel engine after it’s first started is a good idea when the weather turns cold. However, you’ll have to be careful of its downsides too. Here are some negative effects that might happen when you your diesel engine by letting it idle:
Warming up your engine for too long can lead to excessive idling, which causes your engine to burn more fuel than necessary. To avoid this, it’s best to follow the warm-up time recommended by your manufacturer.
Excessive idling can also cause soot to build up faster on your engine’s intake manifold, which can interfere with your engine’s performance and efficiency.
Diesel engines come with a diesel particulate filter (DPF), a filter that captures exhaust soot and reduces emission levels. This filter typically has to be emptied to clear soot buildup every now and then, but excessive idling can cause it to clog up faster.
When done correctly, warming up your diesel engine with a preheater before starting the engine comes with some benefits. Here are a few:
Warming up your diesel engine before starting it allows the air and fuel mixture in the combustion chamber to heat up first. This ensures that the combustion process starts properly.
Those few minutes you spend waiting for your engine to warm up with a preheater make a big difference when it comes to protecting your engine. By warming up your diesel car before firing it up, you’re actually putting less stress on the engine.
A cold engine block with a low coolant temperature tends to produce uncombusted hydrocarbons, carbon monoxide, and other major air pollutants. In contrast, a warmed-up engine block has a smoother combustion process that produces less emissions.
A preheater (whatever kind you use) will help the engine start as if the weather was a lot warmer so that it burns cleaner from the first moment of run time.
Here are a few examples of what happens when you try to start your engine when it’s cold:
While the oil pump is designed to pick up and move the oil quickly to pressurize the oil gallery, it tends to do this a bit more slowly when the oil is very thick.
During colder months, fuel efficiency tends to drop during the first few moments of engine operation. One of the reasons for this is that engine fluids get thicker when it’s cold, and thicker fluid takes longer to reach the optimum temperature for fuel efficiency.
Of course, allowing the engine to warm up first means the engine is running and using fuel, so running the engine to warm it up doesn’t really do much for fuel economy overall, but a warm engine means not burning as much fuel.
Aside from preheating your engine, there are plenty of other ways to help your vehicle warm up. Here are a few tips to help you avoid cold starting your diesel engine:
Glow plugs and manifold heaters heat up incoming air to improve fuel combustion in a diesel engine. Unless a diesel has a manifold heater (like Cummins engines), it’ll typically have one glow plug for each cylinder. Make sure your vehicle’s glow plugs are in good condition, so your fuel combustion can run smoothly.
Block heaters are great if you need additional help in warming up your diesel engine. They’re electrical devices that warm the engine and motor oil when the vehicle isn’t in use. Most diesel trucks come with built-in block heaters that are easy to use. For most block heaters, you just have to plug the heater cord into an extension cord and then plug the extension cord into a socket with the appropriate voltage. But don’t drive off with the cord still connected, or you might ruin something.
Similar to a block heater, a coolant heater can also warm up your diesel engine. It circulates the engine coolant over a heat exchanger, which helps heat the engine, fluids, batteries, and hydraulic tank.
Warming up your diesel engine is important because it allows the oil to heat up, which lets the engine run more efficiently with less stress. The glow plug is a key part that allows diesel engines to heat up during startup. Without them, starting your vehicle in cold weather can be difficult. Need new glow plugs? CarParts.com is here to help.
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