Diesel Exhaust Fluid (DEF) Consumption and Range
Why a DEF tank spans several fuel fills, and never runs it dry.
Example
You enter
- Diesel consumed (gal, 0 = derive from miles/mpg) 200
- Fuel economy (mpg, for range) 6.5
- DEF dose (% of diesel, ~2-3) 2.5
- DEF tank size (gal) 13
You get
- Def used (gal) 5
- Diesel per full DEF tank 520 gal
- Range on one DEF fill 3380 mi
Details, formula, and sources
DEF is metered into the SCR aftertreatment at only about 2-3% of diesel, so def_used = diesel x dose/100 and a full DEF tank covers diesel = def_tank / (dose/100). A 13 gal DEF tank at a 2.5% dose covers 520 gal of diesel = 3,380 mi at 6.5 mpg on one fill (200 gal of diesel burns just 5 gal of DEF); a hard-pulling 3.0% dose shortens it to 433 gal = 2,817 mi. Plan DEF per fuel stop and you haul jugs you do not need or run it dry -- and empty DEF forces an ECU derate to ~5 mph limp-home until refilled. DEF freezes at ~12 F. A planning estimate; the OEM and DEF quality govern.
diesel = diesel_gal > 0 ? diesel_gal : trip_miles / mpg; def_used = diesel x dose/100; diesel_per_def_tank = def_tank / (dose/100); range = diesel_per_def_tank x mpg.
DEF consumption and range model (SCR aftertreatment; the ISO 22241 diesel-exhaust-fluid spec), by name; the OEM and the DEF quality govern the metered rate.
The DEF-to-diesel dose relation is a first-principles ratio; the ~2-3% dose, tank size, and mpg come from the truck and the duty cycle.
Estimate. AHJ and licensed professional govern.
Field names used by the API: diesel_gal, mpg, dose_pct, def_tank_gal, def_used_gal, diesel_per_def_gal, range_mi
- Dose rate DEF runs about 2 to 3% of diesel by volume (default 2.5%)SCR aftertreatment
- Derate an empty DEF tank forces an ECU derate to roughly a 5 mph limp-homeemissions compliance
- Freeze point DEF freezes at about 12 F; the SCR system thaws it in serviceISO 22241