How Much Diesel Exhaust Fluid Do You Need?

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DEF Over the last decade, diesel exhaust fluid (DEF) has quickly become a necessity for the modern transportation fleet. In 2010, the EPA passed more stringent emission standards to reduce the release of NOx and particulate matter from middle- and heavy-duty vehicle engines. At that time and years that followed, selective catalytic reduction (SCR) and DEF helped many diesel-fueled industries meet those standards. In 2014, DEF became even more nationally prevalent when the EPA required off-road equipment manufactured in 2014 and after to use DEF.
If you’re unsure of how much DEF packaging you need for your vehicles and other equipment, keep reading for a couple suggestions and recommendations to purchase the right amount.

How to Estimate How Much You Need

Many DEF suppliers provide online DEF usage calculators to give you an accurate projected amount for your vehicles or equipment. Typically, the estimated amount is calculated using four factors:

  • Number of automobiles in the fleet
  • Average miles per vehicle
  • Average miles per gallon
  • DEF usage rate

The most critical factor you must take into consideration is the rate of DEF your vehicles are using. Most manufacturers of heavy-duty vehicle engines equipped with SCR aftertreatment suggest a usage rate of 3%; in other words, 3 gallons of DEF are used for every 100 gallons of fuel.

It’s recommended that drivers of highway-traveling trucks should refill the DEF tank for every three diesel refills. For smaller vehicles, the DEF tank can be refilled with every oil change. Regarding heavy-duty automobiles, the required amount can be difficult to estimate due to engine configurations, idling times, and the weight of the load being transported.

How to Manage DEF Consumption

For a small fleet of three or four vehicles, a 55-gallon drum should suffice, and larger fleets (10 or more) should require at least one or two 330-gallon totes. Over time, your use of DEF will give you an accurate value of a weekly average use of DEF.

If you are not sure about your exact needs, many DEF suppliers can help you in your estimation and management plan.