Using cheap or contaminated AdBlue fluid might save you a few pounds today, but it can destroy your pump, sensors, and SCR injector tomorrow.
Most breakdowns we see across Leicestershire start with poor-quality fluid or bad storage.
Here’s what to avoid — and how to keep your AdBlue system healthy for the long run.
1. Buying Unbranded or Diluted AdBlue
Genuine AdBlue meets ISO 22241 standards. The liquid should be 32.5 % urea and 67.5 % deionised water.
Many low-cost bottles found online are over-diluted or contaminated with minerals.
That extra “bargain” litre can crystallise inside your injector, clogging the SCR lines and causing
P20E8 or P204F low-pressure faults.
Always buy sealed containers from trusted automotive suppliers. If it smells sharp or cloudy, don’t pour it in — dispose of it safely.
2. Storing AdBlue Incorrectly
AdBlue breaks down in heat and sunlight. Left in a van footwell or workshop corner, it can lose concentration within weeks.
Once that happens, the SCR catalyst can’t convert NOx properly, triggering dashboard warnings like “Check Exhaust System.”
Store sealed containers between −11 °C and 30 °C, away from direct light. In winter, don’t let it freeze solid — repeated thawing separates the urea and ruins the mix.
3. Using Funnels or Containers from Other Fluids
It’s common to reuse a diesel funnel to top up AdBlue — but even a few drops of oil can contaminate the tank.
We’ve seen multiple Mercedes Sprinter systems fail after cross-contamination during refill.
The SCR pump senses foreign residue and shuts down dosing, leading to a “No Start” countdown.
Always use the dedicated blue AdBlue spout supplied with the bottle, and keep it capped when not in use.
4. Leaving AdBlue in the System Too Long
Even genuine AdBlue has a shelf life — usually 12 months after opening.
If your vehicle sits unused, the fluid can crystallise in the injector or return line.
That’s when a full SCR system repair becomes necessary, including flush, filter, and pressure test.
Regular top-ups with fresh fluid help keep seals lubricated and sensors accurate. It’s a simple maintenance habit that avoids costly repairs later.
5. Mixing Different Brands or Additives
AdBlue isn’t a performance additive — adding cleaners or mixing brands can alter its chemical balance.
Some products claim to prevent freezing, but they often contain glycol compounds that destroy the SCR catalyst.
Stick to one trusted brand and never mix fluids that list “enhanced formula” unless approved by the manufacturer.
6. Ignoring Minor Leaks and Crystals
Small white crystals near the tank cap or filler neck may look harmless, but they indicate leaks or air in the dosing line.
Over time, these crystals build up, restrict flow, and trigger the same low-pressure codes found in major faults.
A quick inspection and software reset during a mobile diagnostic visit can stop a small leak turning into a pump replacement.
7. Topping Up Too Late
Waiting until the “500 miles to no start” message appears stresses the pump and causes incorrect dosing cycles.
Refill once the warning first lights up — don’t wait for the countdown.
Our AdBlue delete service is only for vehicles where repair costs exceed value, not as a shortcut for neglect.
Professional Tips to Keep Your AdBlue System Healthy
- Check the expiry date on every bottle before use.
- Keep a 5 L sealed emergency bottle in the cab during long trips.
- Never ignore early SCR or NOx fault codes — they escalate quickly.
- Book a full AdBlue system check once a year for fleet vehicles.
Need Help After an AdBlue Fault?
If your dashboard shows an AdBlue error after topping up, our technicians can diagnose and reset it on-site.
We handle mobile AdBlue repairs across Leicestershire and nearby counties — no tow truck or garage needed.
Book a Mobile Visit or call 07349 821 999 to get help today.
Frequently Asked Questions
Can I mix old and new AdBlue?
It’s best not to. Old fluid can contaminate the new batch and alter concentration levels. Always empty stale fluid before refilling.
How long does AdBlue last once opened?
Around 12 months if stored correctly at moderate temperatures. If exposed to sunlight or frost, discard sooner.
What happens if I accidentally add diesel to the AdBlue tank?
Don’t start the engine — call a technician immediately. The system will need to be drained and flushed to prevent injector and pump damage.
