Updated 2026-11-12
The rule of thumb
For every 100 gallons of diesel, plan on about 2 to 3 gallons of DEF. The exact rate depends on the engine, its emissions calibration, load and idle time. Your engine maker or telematics data will give the real number for your fleet. Published guides use ranges from about 2% up to 5% for heavy loads (NüDef, "Bulk DEF Guide: Totes, Drums, Pumps & Storage" (2026)).
Turn DEF use into a buying plan
| Monthly DEF use | Format that usually fits |
|---|---|
| Under 55 gallons | Jugs or one drum |
| 55 to 300 gallons | Drums or a 275 to 330 gallon tote |
| 300 to 1,000 gallons | Totes on a schedule, or a small bulk tank |
| Over 1,000 gallons | Bulk tank with scheduled tanker delivery |
These bands are a starting point. The right choice also depends on storage space, forklift access and how hot your storage gets. See tote vs drum vs bulk.
Questions
How much DEF does a semi truck use?
At 2 to 3% of diesel, a truck burning 1,000 gallons of diesel a month uses about 20 to 30 gallons of DEF a month.
Why is my DEF use higher than 3%?
Heavy loads, hills, some newer emissions calibrations and certain off-road equipment can run higher. Check with the engine maker.