Diesel engines have a higher flash point than gasoline engines, which makes the chances of ignition very low. So is it actually safe to fill up your diesel vehicle while the engine is running? As a professional diesel engine parts supplier, I decided to dig into this question and outline everything you need to know about filling diesel with the engine on.
Why Do People Fill Diesel with the Engine Running?
Before answering whether or not this is safe, it’s important to understand why people choose to keep their diesel engines running during refueling. There are a few key reasons:
Convenience – It’s simply easier not to have to turn off and restart the vehicle. This seems to be the most common reason.
Avoid Turbo Heat Soak – After running hard, some drivers like to keep the turbocharger cooling down before oil flow is cut off when shutting off the engine.
Cold Weather Operation – In very cold climates, drivers may not want to risk the vehicle not restarting if they shut it down.
So in many cases, there are logical reasons behind the choice to keep diesel engines running during fueling rather than simply being careless.
Can You Fill Diesel with Engine Running?
Yes, in most cases, it is safe to pump diesel fuel into a running diesel engine. The chances of the fuel igniting are extremely low due to the high flash point of diesel fuel, lack of sparks generated by a diesel engine, and low volatility of diesel vapor.
As long as there are no nearby gasoline or propane pumps, and you are filling the tank that is NOT actively being drawn from, risks are minimal. It’s smart to avoid this practice around older diesel vehicles however. So ultimately, yes you technically can safely fill up your diesel pickup, truck, or equipment while leaving the engine running. It’s reasonable to do this regularly.
Is Filling Diesel with the Engine On Safe?
Now to the main question: is it actually safe to pump diesel fuel into a running diesel engine?
The answer is generally yes, it is safe in most circumstances.
Here’s why:
- Diesel fuel has a much higher flash point compared to gasoline, typically between 126°F and 205°F. This temperature is difficult to reach from a running engine.
- There is little risk of igniting fumes like there would be with gasoline. Diesel vapor doesn’t ignite nearly as easily.
- No electric sparks are generated by a running diesel engine, eliminating another ignition source.
However, there are a few precautions worth mentioning:
- Make sure no gasoline or propane pumps are nearby, as diesel fumes could ignite those.
- Don’t fill up the tank the engine is actively drawing fuel from. This can lead to stalling.
- Be cautious doing this with older diesel vehicles, as their fuel systems may allow for easier ignition.
So all things considered, filling up a modern, well-maintained diesel engine with it running appears to be reasonably safe in most situations. But it’s smart to take basic precautions as well.
Best Practices for Refueling Your Diesel Truck
Even though the risks are low, many manufacturers and operators still recommend shutting off your diesel engine while refueling. This follows procedural safety best practices.
Here are some other tips:
- Confirm diesel is the only fuel available on-site before keeping the engine running.
- Cool your turbocharger for 1-2 minutes after hard driving by idling before shutting off.
- If extreme cold weather, weigh whether restarting issues outweigh the (small) fueling risks.
- Always pay attention during fueling, rather than walking away from a running truck.
Following these simple guidelines will keep risks to an absolute minimum while refueling your diesel, whether you shut it down or leave it running.
Conclusion
While the chances of an explosion or ignition event are extremely low, there is technically a higher risk when pumping diesel fuel into a running engine compared to shutting it down. For most drivers this added risk is negligible, but for facilities that fuel a large diesel fleet, procedural safety should rule.
The most important thing is to be aware of your specific situation and the location of any gasoline or propane fuel pumps nearby that could pose a slight risk. As long as you use sound judgment, fill up your diesel truck or equipment with the engine running if it makes your day more convenient!