AdBlue and diesel don’t mix

By: Steve Skinner

Drivers putting AdBlue into diesel tanks and vice versa is a recipe for disaster

AdBlue and diesel don’t mix
The AdBlue and diesel tanks are clearly marked on this bus

AdBlue is the most recognised form of diesel exhaust fluid (DEF), which is needed for selective catalytic reduction (SCR) emissions control in many modern engines.

SCR is used in many Euro 4 and Euro 5 buses in Australia to control oxides of nitrogen (NOx), which can harm the respiratory system.

The other main method for controlling NOx is exhaust gas recirculation (EGR).

It’s widely expected that the next round of emissions standards – Euro 6 – will require at least SCR, if not both EGR and SCR, for most buses and trucks.

So SCR is on the rise, and unfortunately the anecdotes of bus and truck drivers getting AdBlue and diesel mixed up seem to be increasing as well.

Peter Angus is field support manager for Mercedes-Benz buses and coaches in Australia, and he was one of the keynote speakers at the BusVic conference in Melbourne in July.

"It has happened to several companies that people go and put diesel in the AdBlue tank, or AdBlue in the diesel tank," lamented Angus.

"They forget they’ve got the wrong gun in their hand; it’s night-time and they want to go home.

"If you put AdBlue in your diesel tank you will find out very quickly. The vehicle will probably travel maybe 50 yards up the road and the filter will block solid and you’ll get no fuel into the system.

"If you put a small amount in that’s good; if you put a big amount in, that’s very bad, because that starts to go through the injection system and you might be up for a very costly repair."

Luckily, Angus says that because AdBlue crystallises when it meets water, it generally gets blocked in the fuel filters.

"I haven’t seen it go through an engine as yet, but after you get told someone has put 110 litres of AdBlue in a diesel tank, you wonder how far it goes."

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