Diesel in the AdBlue tank
Diesel in the AdBlue tank is the severe direction of this mistake. Do not start the engine and do not let the dosing system run. Even a small quantity contaminates the whole SCR circuit. Call 01293 248666 for an honest assessment before anything is quoted.
The SCR circuit is closed, precision and low tolerance: a tank with an in-tank heater and level sender, a metering pump, heated lines and a dosing injector that sprays a fine mist into the exhaust ahead of the catalyst. It is specified for one fluid, AUS 32 to ISO 22241, and nothing else. Diesel is a hydrocarbon. It coats every internal surface it touches, it does not rinse out with water, and it does not decompose to ammonia. Passed to the catalyst it poisons the washcoat. This is why it is rarely a drain-and-go job.
Call 01293 248666 From just £89 call-out fee
Diesel in the AdBlue tank — the severity verdict
| Severity | Component risk Frequently needs SCR component work rather than a drain. Quoted before a technician travels. |
|---|---|
| What went where | Diesel in the AdBlue tank |
| Direction | Into the AdBlue tank |
| Typical cost | £260–£750 typical total, from a £89 call-out |
| Time on site | About 90 minutes |
| Call-out | From just £89 call-out fee |
| Helpline | 01293 248666, 24 hours |
£89 is the call-out. An AdBlue tank drain and flush is quoted on the phone before a technician travels. If the SCR system needs component replacement — dosing injector, pump, tank or catalyst — that is separate, and you will be told before any work starts. If this is a job we cannot fix at the roadside, we will tell you that on the phone rather than after we arrive.
What to do right now
- Do not start the engine. The dosing pump runs on many vehicles as soon as the system is awake.
- If it is already running, switch it off now rather than driving to a garage.
- Do not top it up with AdBlue to dilute it. Dilution does not undo hydrocarbon contamination of the pump and lines.
- Call 01293 248666 and say how much diesel went in and whether the engine has run since.
What a technician actually does
Tank drained and the hydrocarbon layer captured separately, tank and lines flushed with demineralised water and then with AUS 32, the metering pump and dosing injector assessed, refill with fresh ISO 22241 fluid, and a system test with fault codes read and cleared. Where the pump, injector, tank or catalyst needs replacement, that is identified and quoted before it is done.
Why this is not the same job as the other direction
This is contamination of the SCR dosing circuit — tank, metering pump, heated lines, dosing injector and potentially the catalyst. It is not the fuel system, and it is not the cheaper job. Anyone quoting a flat drain price for this has not looked at the system.
Common questions
Is this just a drain like AdBlue in the diesel tank?
No, and anyone who tells you it is has not looked at the system. That direction is a fuel-side drain. This one is hydrocarbon contamination of a precision dosing circuit, and it frequently needs component work.
Can I dilute it with more AdBlue?
No. Diesel does not dissolve in AdBlue and it does not stop coating the pump internals and the injector because there is more fluid around it. Topping up adds cost to the drain.
Will the SCR catalyst need replacing?
Only if contaminated fluid has actually been dosed into the exhaust — which is why not starting the engine matters so much. If the system never ran, the catalyst is usually untouched.
What customers say
4.8 out of 5 from 2,190 Trustpilot reviews. What reviewers mention most is that the technician stayed calm and professional with a driver who was embarrassed and stressed, and that somebody arrived when they said they would.
The most common criticism is price. People do not expect a wrong-fluid job to cost what it costs, and that is a fair complaint to publish rather than bury. The answer is the From just £89 call-out fee, a quote given on the phone before a technician travels, and being told when a job cannot be done at the roadside rather than after somebody has arrived and charged for the visit.
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Where we cover
Who you are dealing with
AdBlue in Fuel is a service by Forecourt Assist. Forecourt Assist is a trading name of Fuel Fixer Ltd, company no 08520551, registered at Fairway House, Portland Road, East Grinstead, RH19 4ET, a company of Fuel Fixer International. Fuel Fixer International is owned by Stockbridge Capital Holdings.
Reference: Diesel particulate filter (Wikipedia).
Across the Fuel Fixer network
AdBlue in Fuel is a service by Forecourt Assist, a brand of Fuel Fixer International, owned by Stockbridge Capital Holdings. The full group directory is at forecourtassist.co.uk/network.