Adblue (urea) diesel fuel additive explained | AutoExpert John Cadogan

AdBlue goes into your diesel engine’s exhaust, and fewer toxic emissions come out - that’s what it does. But on the consumer front, can the carmaker compel you to use their own brand of AdBlue in your car? That’s next.
This report is inspired by a damn fine recent question from Robert W - and I’m tipping he is not alone:
I went for a service at my MB Dealer. I told him I fill up with AdBlue at the BP truck pump. He said I should not use it because it crystallises. He told me I should only use MB Adblue, but of course it is a lot dearer. At the fuel pump it is only 90 cents a litre. So, is Adblue that different between the petrol station and what MB sells?
Robert is the owner of a Mercedes-Benz ML 250 diesel - so I know you’ll join with me in extending my sincere sympathies to Robert on this. An ML 250. Nobody deserves that.
Frankly, what Robert was told sounds like illegal, shady advice from a pretty dodgy and/or ignorant dealer to me. It reinforces my belief that a car dealership is not the kind of place one should attend to procure advice.
The ACCC is very clear that Mercedes-Benz (or any other carmaker) cannot mandate the use of genuine parts or consumables used to service or repair the vehicle. That would be illegal. There is, however, an obligation that the parts you do use be fit for purpose.
A simple example is: The oil filter on your car. It does not have to be the carmaker’s filter, but you must use a filter designed for that engine. Same for the oil used to service the vehicle, or a replacement radiator used in crash repair - whatever.
My understanding is that AdBlue is trademarked by the German Association of the Automobile Industry - meaning that anything marketed as AdBlue is just a 32.5 per cent solution of urea in de-ionised water. It’s also called AUS32 - for aqueous urea solution, 32.5 per cent.
As chemicals go, AdBlue is not rocket science. Not even close. It’s not 224 trimethly pentane, is it? (Look it up.) AdBlue is clear, non-toxic and safe to handle, easy to make and store, and it’s classified under the ‘minimum risk’ category for transportable fluids.
Anyhoo … AdBlue goes to war against oxides of nitrogen in your exhaust. Oxides of nitrogen are toxic chemicals that are respiratory tract irritants. Very bad for you. AdBlue decomposes them to harmless nitrogen gas and oxygen gas. You use up to five litres of AdBlue for every 100 litres of diesel. And the car will not run if you run out of AdBlue - so, don’t leave it too long with the warning light on.
It seems to me that anything legitimately called AdBlue would be compatible with any Merc that requires AdBlue - if it has the AdBlue trademark it complies with the ISO 22241 quality standard - regardless of whether you pick it up at a filling station or the Mercedes-Benz dealership.
To see what the mothership said on this, I scoured Mercedes-Benz’s Australian website. They do have a page on AdBlue, which is currently required on S-Class, G-Class and ML-Class. Basically, any Benz with the BlueTEC badge needs glorified piss to run.
Happily enough, nothing on the Merc AdBlue reference page says you must use the genuine Mercedes-Benz AdBlue solution - presumably because requiring that would be illegal. They do suggest it. (That’s allowed.) So, Robert, it seems to me that you may legitimately power ahead with non-genuine glorified pee in your glorified luxury German SUV. So that’s nice.
Of course, this is unlikely to make your local dealer very happy, in respect of his unjustified billion per cent AdBlue markup. (Actual ACCC determination of average dealer profit margin in the servicing business across all brands: 64 per cent. Service is the most profitable part of a new car dealership. And they do so pump up the price of the consumables.)