Size a diesel exhaust fluid order
DEF dosing follows diesel consumption, not distance. Enter your fleet's diesel volume or distance and duty cycle to get the litres, drums and cartons you actually need.
Based on ≈ 1,000 L of diesel at a 5 % dosing ratio.
- 10 L drums required
- 5
- Cartons (2 drums each)
- 3
DEF dosing tracks diesel consumption rather than distance, because the SCR system meters urea in proportion to the nitrogen oxides produced. Plan replenishment on diesel volume, not on a fixed interval.
View diesel exhaust fluidThree things fleets get wrong with DEF
Planning on distance instead of diesel
It is tempting to budget DEF per kilometre, but SCR systems dose in proportion to the nitrogen oxides produced, which tracks fuel burned. A truck that spends its life in traffic burns far more fuel per kilometre than one on a motorway, and its DEF consumption rises with it. Plan on diesel volume.
Storing it like oil
Urea degrades above about 30 °C and releases ammonia, so the concentration drifts below the ISO 22241 specification. Drums sitting in the sun, or in a metal container on a dock, can go out of specification before they are opened. Keep DEF between 0 and 30 °C, out of sunlight, in sealed containers, and do not store it in galvanised or bare aluminium vessels — urea attacks zinc and picks up metal ions that poison the SCR catalyst.
Stretching a drum
Diluting DEF with water to make it go further is the fastest way to trigger a derate. Modern SCR systems measure urea concentration from the dosing behaviour and will log a fault. There is no legitimate low-strength DEF — the specification is 32.5 % or it is not DEF.
Typical dosing ratios we use
These come from real fleet behaviour rather than theory, and they are what the calculator applies.
Quick reference
- · Long-haul Euro VI truck — about 5 % of diesel volume
- · Long-haul Euro V truck — about 4 %
- · Urban delivery, stop-start — about 6 %
- · Intercity bus — about 5 %
- · Off-road and construction — about 4 %