How Much DEF Does a Truck Use?

DEF is a urea-based solution that helps to reduce emissions of nitrogen oxide (NOx) from diesel engines. When used in conjunction with a Selective Catalytic Reduction (SCR) system, DEF can help to reduce NOx emissions significantly. With the price of diesel fuel rising, more truck drivers are looking for ways to save money at the pump. One way to do that is to switch from using regular diesel fuel to using Diesel Exhaust Fluid, or DEF.

A typical DEF tank on a heavy-duty truck can hold up to 100 gallons (378 liters) of DEF. The average truck uses about 0.67 gallons (253 ml) of DEF per 100 miles (161 km). If you’re considering switching to using DEF in your truck, it’s important to remember that DEF is a consumable product. You’ll need to purchase it regularly and budget for its cost. A gallon of DEF costs about $0.60 per gallon (or $0.15 per liter). So, if you’re driving a typical heavy-duty truck with a 100-gallon (378 liters) DEF tank, you can expect to spend about $60 on DEF each time you fill up your tank.

How Many Miles Will 1 Gallon of DEF Last?

Most DEF tanks require one gallon of DEF for every 50 gallons of diesel fuel, and one gallon will generally last between 300 and 500 miles. It is essential not to allow the DEF tote to become empty. It should be refilled when 2-3 inches of DEF remain in the tote. If the tank is allowed to become empty, it can cause irreversible damage to the DEF pump and system. In addition, it is essential to use only high-quality DEF that meets the American Petroleum Institute (API) standards. Using a lower-quality DEF can clog the system and reduce its efficiency. Ultimately, following these guidelines will help ensure that your vehicle gets the most miles per gallon of DEF.

How Much DEF Does a Truck Hold?

Most light-duty and medium-duty trucks will have a DEF tank that can hold between three and five gallons. This is a relatively small amount of DEF compared to the truck’s fuel tank size, but it is still enough to add extra weight to the vehicle. The price of def per gallon can range depending on the size of your truck. It can hold anywhere from 25 to 80 gallons of DEF. On average, DEF weighs about 9 pounds per gallon. So, a full DEF tank on a truck can weigh anywhere from 27 to 45 pounds. This may not seem like much, but it can add up over time, especially if the truck is carrying a heavy load. In addition, the weight of the DEF can affect the truck’s suspension and handling. Thus, it is essential to monitor the level of DEF in the tank and only fill it up when necessary. Doing so can help keep your truck running smoothly and prevent potential problems from carrying a heavy load. It is important to check your DEF levels regularly and top them off when needed to avoid any issues with your truck’s emissions system.

How Often Do You Put DEF in a Diesel?

The diesel fuel helps to lubricate the engine and keep it running smoothly. However, diesel engines also produce emissions that can harm the environment. To help reduce these emissions, many diesel engines are now equipped with a diesel particulate filter (DPF). The DPF traps soot and other particles produced by the engine, and it is eventually necessary to clean or replace the filter. One way to clean the DPF is to use a diesel exhaust fluid (DEF). DEF is sprayed into the exhaust system, which reacts with the soot particles and breaks them down into harmless gases. As a result, DEF helps to reduce emissions and keep the DPF clean. Most DEF tanks need to be refilled once every 3 to 4 times you refuel with diesel fuel.

How Often Is DEF Needed?

Generally, you need to replace DEF every third or fourth time you fill your gas tank. However, if you have a smaller gas tank or consume DEF at a rate of 2–3% relative to your fuel consumption, you may need to replace it more frequently. Ultimately, it’s essential to check your DEF level regularly and top it off as necessary to ensure your vehicle runs efficiently.

What Happens if You Run Out of DEF?

If caught without DEF, you’ll first notice a loss of power. Your machine will run less efficiently, and you may eventually lose all power altogether. In addition, your emission control system will no longer be able to function properly, causing your exhaust to turn black. Not only is this bad for the environment, but it’s also against the law in many states. Depending on how long you’re without DEF, you may also start to see damage to your engine. So, while running out of DEF may not seem like a big deal at first, it can cost you a lot of money in the long run.


A DEF is integral to a diesel engine’s emission control system. It helps to reduce emissions and keeps the engine running smoothly. Most DEF tanks must be refilled once every three or four times you refuel with diesel fuel. Using DEF regularly can help prolong your engine’s life and avoid costly repairs. Therefore, it is essential to check your DEF level regularly and top it off as needed.

About the author, Laurence Perkins