Sylvie Willis
It is a common practice for some drivers to keep their diesel engines running while refuelling. While this may seem counterintuitive, there are several reasons behind this practice. Firstly, diesel engines have a higher flash point compared to gasoline engines, making them less flammable and reducing the risk of explosions or fires during refuelling. Secondly, diesel engines experience significant metal-on-metal wear during start-up, and keeping the engine running helps keep the turbo lubricated and prevents heat-soaking. Additionally, some drivers may want to maintain their cabin HVAC system or keep their battery charged through the alternator, which requires the engine to keep running. However, it is important to note that idling a diesel engine wastes fuel and can lead to higher costs, especially with rising gas prices. Furthermore, running a diesel engine with low fuel levels can cause serious damage to the fuel system and injectors, making it a potentially costly mistake.
| Characteristics | Values |
|---|---|
| Safety | Diesel has a high flash point, so there is a significantly lower risk of refueling compared to gasoline. |
| Engine life | Engine life is measured in heat cycles. Most metal-on-metal wear occurs on start-up. Keeping the engine running keeps the turbo lubricated and prevents heat-soaking. |
| Engine temperature | Keeping the engine running keeps the temperature within the peak performance range. |
| Battery life | The alternator recharges the battery while the engine is running. |
| Engine cooling | Keeping the engine running allows the turbo to cool down. |
| Fuel system | Running low on diesel can damage the fuel system as sediment builds up at the bottom of the tank. |
| Fuel efficiency | Idling uses less fuel than restarting the engine. |
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What You'll Learn
It's safer than turning it off immediately after a heavy load
It is safer to keep a diesel engine running, especially after it has been under a heavy load, because the turbocharger needs to cool down. The turbocharger is cooled by oil, so if the engine is shut down, the oil flow will stop, and the turbocharger will not be able to cool down. This can lead to metal components of the engine welding together due to the high temperatures.
Additionally, engine life is measured in heat cycles, and most metal-on-metal wear occurs during engine startup. By keeping the engine running, you avoid the need for a startup cycle, reducing wear and tear on the engine. Diesel engines are also designed to maintain a specific temperature range for peak performance, and turning off the engine will cause it to cool down and exit this range. Restarting the engine will require another performance ramp-up, resulting in wasted fuel and reduced performance.
Furthermore, diesel fuel has a high flash point, typically between 52 and 96 °C (126 and 205 °F). This means that it is less flammable than gasoline and has a significantly lower risk of ignition during refueling. While there are still safety concerns, such as the creation of static electricity when entering and exiting the vehicle, the risk of engine damage due to high temperatures after a heavy load is a more significant concern.
However, it is important to note that idling a diesel engine wastes fuel and increases operating costs. Additionally, in some work environments, it may be mandatory to shut down all vehicles and heavy equipment during refueling, regardless of fuel type. Therefore, while keeping a diesel engine running after a heavy load may be safer for the engine, it is not always the standard practice and may depend on specific circumstances and regulations.
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Minimises engine wear and tear
One of the main reasons diesel engines are kept running while refuelling is to minimise engine wear and tear. Engine life is measured in heat cycles, and most metal-on-metal wear occurs during start-up. By keeping the engine running, you maintain the temperature within the peak performance range. This prevents the need for another performance ramp-up when the engine is turned back on, saving fuel and improving performance.
Additionally, the turbocharger in a diesel engine is cooled by oil. If the engine is shut down directly after a heavy load, there is no oil flow, resulting in hot metal against hot metal. This can cause significant damage, and even weld the turbocharger together. Keeping the engine running while refuelling allows the turbocharger to remain lubricated and prevents heat-soaking.
Furthermore, running low on diesel can also damage the fuel system. The poorest-quality fuel, which is often full of sediment, settles at the bottom of the tank. When the fuel level is low, this sediment can be pulled into the fuel system, clogging or breaking the fuel pump, filter, rail, and injectors. This can lead to costly repairs and extended downtime.
Keeping the diesel engine running while refuelling helps to minimise engine wear and tear by maintaining optimal temperatures, preventing damage to the turbocharger, and reducing the risk of fuel system issues caused by low fuel levels.
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Diesel has a high flash point, so less risk of explosion
Diesel engines are often kept running while refuelling to prevent damage to the engine. Diesel has a high flash point, typically between 52 and 96 °C (126 and 205 °F), which means it has a significantly lower risk of explosion compared to gasoline. Gasoline is highly combustible and can easily ignite at room temperature, but diesel is not as flammable and requires much higher temperatures to ignite. This high flash point of diesel fuel reduces the risk of explosion during refuelling, making it safer to keep the engine running.
The practice of keeping diesel engines running during refuelling is also influenced by the design of the coolant system. Auto manufacturers design coolant systems to maintain the engine within an optimal temperature range for peak performance. When the engine is turned off, it cools down, dropping below this temperature range. As a result, when the engine is restarted, it requires time and fuel to return to the peak performance temperature range. By keeping the engine running during refuelling, the temperature is maintained, preventing fuel waste and ensuring optimal performance.
Additionally, for tractor-trailers and similar large vehicles, it is common for the engines to be designed to run continuously, 24 hours a day. These engines are built to withstand extended periods of operation, and turning them off and on repeatedly can be more detrimental than keeping them idling.
Furthermore, the process of restarting a diesel engine after it has been turned off can be more stressful on the engine than simply letting it idle. This is especially true for turbocharged diesel engines, where keeping the engine running helps to cool the turbo and prevent metal-on-metal wear. If the engine is turned off after a heavy load, the lack of oil flow can lead to issues with the turbo, and in some cases, cause the turbo to weld itself together.
While keeping a diesel engine running during refuelling may have its advantages, it is important to consider safety precautions. Some sources suggest that running an engine during refuelling can create safety hazards, such as reduced awareness of potential issues, the generation of static electricity, and increased difficulty in hearing problems with the vehicle. Therefore, it is crucial to follow safety protocols and be mindful of potential risks when refuelling a diesel engine, even with the reduced risk of explosion due to diesel's high flash point.
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To keep the cabin HVAC on
Keeping a diesel engine running while fuelling is a common practice, and one reason for this is to maintain the cabin HVAC system. This is especially relevant for truckers who sleep in their vehicles, as they rely on keeping the engine running to keep the cabin HVAC on.
The HVAC system in a vehicle works more efficiently when the engine is running. When the engine is turned off, the HVAC system also shuts down, and the cabin temperature can become uncomfortable. By keeping the diesel engine running, the cabin remains at an ideal temperature, providing comfort for the driver and any passengers.
In addition to comfort, there are other benefits to keeping the engine running. When the engine is idling, the battery receives a small charge from the alternator, which is essential for keeping the battery healthy and avoiding frequent replacements. Idling also helps prevent the turbocharger from cooling down too quickly, which can cause issues with the turbo and engine.
While idling a diesel engine can be beneficial in certain situations, it is important to consider the potential drawbacks. Idling for extended periods can lead to increased fuel consumption, higher emissions, and even engine damage. Therefore, it is generally recommended to keep idling time to a minimum, especially when not necessary for maintaining cabin comfort or preventing turbocharger issues.
In summary, keeping a diesel engine running while fuelling can be advantageous for maintaining cabin HVAC, battery health, and turbocharger performance. However, it is important to balance these benefits with the potential negative impacts on fuel efficiency, emissions, and engine health.
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To keep the battery charged
Keeping a diesel engine running while refuelling can be a means of keeping the battery charged. The alternator is a small engine that feeds off the main engine's power and recharges the battery. When a truck is idling, the battery gets a small charge. This is especially important for truckers who sleep in their vehicles, as they need to keep the cabin HVAC on. Idling is the least impactful thing on the engine, compared to the stress of getting a diesel engine started after turning it off.
Another reason to keep a diesel engine running is that engine life is measured in heat cycles. Most metal-on-metal wear occurs on start-up, and keeping the engine running keeps the turbo lubricated and prevents heat-soaking. Diesel parts are expensive, and it takes very little fuel to keep a diesel engine idling.
It is worth noting that while some people keep their diesel engines running to keep the battery charged, others argue that idling wastes fuel and money. Additionally, it can be dangerous as it may be difficult to hear any issues with the vehicle, and getting in and out of a running vehicle can create static electricity.
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Frequently asked questions
Yes, it is safe to keep a diesel engine running while refueling as diesel fuel has a high flash point and is less combustible compared to gasoline. However, it is still recommended to shut off any vehicle or heavy equipment while refueling in case of any issues.
Keeping a diesel engine running while refueling helps to minimize the on/off cycle and keep the engine within its peak performance temperature range. This reduces fuel wastage and improves performance.
Yes, keeping the diesel engine running helps to keep the cabin HVAC on, which is important for truckers who sleep in their vehicles. It also keeps the battery charged by allowing the alternator to constantly recharge it.
While it is generally safe to keep a diesel engine running while refueling, some potential issues include reduced fuel efficiency, difficulty hearing any issues with the vehicle, and increased safety risks due to getting in and out of the vehicle.
