Mixing diesel and AdBlue a recipe for trouble

By: Steve Skinner

Mercedes-Benz expert says several companies have reported people putting diesel in the AdBlue tank.

Mixing diesel and AdBlue a recipe for trouble
Mercedes-Benz field support manager Peter Angus.


A technical expert on heavy vehicles has warned against drivers mixing up diesel with AdBlue.

Mercedes-Benz field support manager Peter Angus used his appearance this year's BusVic conference in Melbourne to caution attendees about the dangers of mixing the fluids.

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

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

"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."

In fact, Owner//Driver has heard of a $15,000 repair job on a truck from such a balls-up.

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," he says.

On the flipside – diesel contamination of AdBlue – Peter Angus advocates the use of testing strips at each SCR system service, to make sure there is no diesel in the AdBlue circuit.

He says if diesel is detected, you can drain your tank and flush it out and hopefully you haven’t ruined the pump.

Meanwhile A-Flo national sales manager Dean Cook points out that you’re not normally able to fit a high flow diesel nozzle into an AdBlue tank spout.

To stop the reverse problem of putting AdBlue into a diesel tank, A-Flo offers magnetic nozzles to pair with magnets in AdBlue tanks. The AdBlue will only flow if there is a magnet to open the nozzle mechanism.

Most truck DEF tanks these days have magnets, but A-Flo supplies magnets to Shell service stations for those truckies who discover the hard way that there isn’t one on their truck.

Most truckstop AdBlue nozzles are magnetised and there are an increasing number of AdBlue bowsers at truckstops.

If there is no magnet in the truck tank, the nozzle will keep flicking off. So too if it’s a weak or old magnet, Cook says.


"They forget they’ve got the wrong gun in their hand."Has this happened to you or someone you know?

Posted by Owner Driver on Thursday, 6 August 2015

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