Diesel Exhaust Fluid (DEF)

How Does DEF Work?

DEF works through a process called Selective Catalytic Reduction (SCR). In 2010, SCR was mandated in diesel engines as an environmental initiative. SCR uses a catalyst system containing ammonia to break down Nitric oxide (NOx) emissions. NOx gases are the leading cause of air pollution. SCR can break down those emissions once DEF gets sprayed into the exhaust stream.

SCR has been around for nearly half a century and it was first used in the power generation industry to reduce oxides of nitrogen from coal-fired power plants.

How Often Does DEF Have to Be Refilled?

For typical trucks and SUVs, a tank of DEF needs to be refilled about as often as changing your oil. For semi-trucks, refill is required a lot more frequently due to the mileage on your truck.

How Much DEF Will My Vehicle Consume?

DEF consumption is usually measured in terms of the amount of “dose rate” of diesel your vehicle consumes. Therefore, if you are driving a long distance or use your vehicle often, you will use much more DEF than someone who works locally. Usually, they say that DEF tanks are to be refilled every 4,000 to 10,000 km, but that depends on the size of the vehicle and its use.

Does DEF Freeze During Cold Weather?

DEF freezes at -11 degrees Celsius, which is bound to happen in our Canadian winters! Typically, DEF thaws on its own from the heat of the engine and does not impact the functioning of the vehicle. Upon starting the vehicle, the SCR system provides heat to DEF tank, where it begins to thaw. As with any water-based fluid, DEF expands when it is frozen. Before shutting down the vehicle, wait a minute prior to turning off the battery. This delay will allow the fluid to drain out of the hoses and into the DEF tank.

How Will I Know if I’m Low On DEF?

Similar to when you are low on gas, you’ll know when you are low on DEF. All engines designed with SCR also come equipped with a gauge to display the DEF fuel levels. If you run out of DEF, lights will flash to notify you. Unlike gas, if you run out of DEF, it won’t impact the functioning of your vehicle.

What Are the Benefits Of DEF?

  • Reduced pollution- The main reason selective catalytic reduction was introduced was to help the environment. Diesel has been known to emit poisonous NOx emissions, typically blamed for causing acid rain and the greenhouse effect. With DEF turning the emissions into nitrogen and water, this is much more environmentally friendly.
  • Reduced maintenance- Engines designed with SCR technology have less wear and tear on their vehicles than those without, reducing the need for maintenance. Reduced maintenance also means that your vehicle is less likely to break down.

At Roma Fuels Ltd, we have been a family owned and operated business since 1968, fueled by exemplary customer service. We now offer DEF in the following formats:

  • Jugs (9.4L)
  • Drums (202L)
  • Bulk (1200L totes); or
  • Direct to equipment (wheel to wheel).


Other larger tank options are also available for customized solutions.

Avoid damage. Avoid the next tow. Keep your diesel engine running. Contact us today for more information or call us at 1-877-656-4189.