ISO 22241
ISO 22241 is the standard that defines AdBlue: 32.5% high-purity urea in 67.5% demineralised water, known as AUS 32, with strict limits on impurities. Fluid outside it is not AdBlue, whatever the label says.
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ISO 22241 — the detail
What the standard specifies
Concentration is only the headline. ISO 22241 also caps biuret, aldehydes, insoluble matter, phosphate and a list of metals — calcium, iron, copper, zinc, chromium, nickel, aluminium, magnesium and sodium — at parts-per-million levels, and it covers handling, storage and transport as well as composition.
Why the impurity limits matter more than the concentration
The dosing injector sprays a fine mist through a small orifice at exhaust temperature. Insolubles block it. Dissolved metals deposit at the tip and poison the catalyst washcoat downstream. Those limits are not bureaucratic; they are the difference between a system that lasts and one that does not.
Why 32.5%
It is the eutectic concentration — the mix that freezes at the lowest temperature, around −11 °C. That is why vehicle tanks and lines are heated and why the specification is a formulation rather than a target you can average back to by adding water or concentrate.
AdBlue and the trademark
AdBlue is a registered trademark of the VDA, licensed for fluid meeting ISO 22241. A container that says 'urea solution' without stating conformity to the standard is telling you nothing about its impurity content.
Storage and shelf life
The standard covers storage because the fluid degrades: urea hydrolyses slowly to ammonia and the rate rises with temperature. Manufacturers quote shelf life against a storage temperature band rather than a flat date.
Common questions
Is all AdBlue the same?
Certified fluid meets the same standard, so within certification, yes. Uncertified urea solution is a different product regardless of what the bottle is shaped like.
Can I make my own from urea and water?
No. Agricultural and industrial urea carries impurity levels far above what the standard permits, and those impurities deposit at the injector and poison the catalyst.
How do I check a container is certified?
Certified product states conformity to ISO 22241 on the container. Price is not a signal either way.
£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.
More explainers
If something has already gone wrong
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.
Who you are dealing with
This site is published by Forecourt Assist, which operates AdBlue in Fuel. 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. The group, Fuel Fixer International, is owned by Stockbridge Capital Holdings.
Reference: VDA — AdBlue trademark holder.
Across the Fuel Fixer network
These are sister brands of the same company, not unrelated sites. Forecourt Assist keeps the canonical list at forecourtassist.co.uk/network rather than duplicating it here.