AdBlue Consumption Too High? Five Causes and On-Site Checks

Your van gulped a full 10-litre can of AdBlue last week, and the dash already wants more.
At £15 a fill that stings, but the real worry is a looming no-start lock if the SCR ECU believes fluid is vanishing without lowering NO_x.
RAC’s 2025 fleet study shows abnormal AdBlue use almost always traces back to five repeat offenders.
Good news: four of the five can be diagnosed kerb-side with a cheap scanner and a flashlight.
Follow the checks below before ordering pumps or injectors; you may solve the thirst in under 30 minutes.

What counts as “too high”?

On Euro-6 vans the dosing rate sits near 3 % of diesel burn.
A Sprinter running 30 mpg should sip 1 L of AdBlue every 600 mi.
Anything worse than a litre per 300 mi flags an over-dosing fault.
Live data item SCR_dose_qty should read 0.07–0.09 g/s at 2 000 rpm cruise; numbers above 0.12 g/s mean the ECU is compensating for a leak, crystal blockage or false NO_x reading.

Five common causes and on-site checks

• Cracked return hose – look for wet streaks on the tank brace. The pump sees pressure drop, doubles dosing to maintain NO_x target.
• Blocked injector tip – chalky crust narrows the orifice; ECU stretches pulse-width to keep flow, burning 50 % more fluid. Borescope the tip through the shield.
• Failing NO_x sensor – when the downstream sensor drifts high, the ECU sprays extra urea. Live NO_x > 200 ppm at idle hints heater drift.
• Over-concentration – DIY top-ups from open drums drive urea above 35 %. The ECU doses proportionally to concentration, so flow rises. Refractometer reading above 1.40 means drain and refill.
• Software corruption after jump-start – low voltage scrambles the SCR map, multiplying requested dosing. Flash the latest file via Autotuner to restore the correct table.

10-minute diagnostic routine

1 – Plug a scanner into the OBD port and note SCR_dose_qty.
2 – Key off, remove the blue return hose and feed it into a measuring jug, key on again.
If more than 30 mL returns in 60 s at idle, the hose or injector leaks internally.
3 – With engine off, measure fluid level. Drive 20 mi urban loop; re-measure. More than 0.8 L drop signals real over-use.
4 – Read downstream NO_x ppm at idle; over 300 ppm suggests sensor drift.
5 – If ppm is normal yet dosing high, load the latest SCR file; corruption resets pulse-width scalars to defaults.

Service options once you’ve found the cause

Leaking hose or injector: replace £22 hose kit, £48 nozzle; clear codes.
Sensor drift: swap downstream NO_x sensor (£190–£320) then run the learning routine.
Over-concentrated fluid: drain, rinse and refill via the spill-proof top-up guide.
Corrupted map: mobile flash takes 15 min and restores factory dosing.
If none of the above solves the thirst, book a deeper system flush via the mobile AdBlue service hub.

Frequently asked questions