by Chris Manescu

What’s Up With My Exhaust Fluid?

Diesel Exhaust Fluid (DEF) plays a critical role in meeting emission compliance requirements. But if any common vehicle fluids (including water) are accidentally added to the DEF tank, the Diesel Exhaust Fluid will be contaminated, leading to damage of system components and making the emission reduction properties of the system ineffective.

Some ways that contaminated DEF can be detected include the following:

• DEF is usually clear, but when it comes into contact with copper or brass it will appear “light blue,” and if it comes into contact with steel or galvanized steel, it will appear to be a “rusty” color.
• DEF is heavier than diesel fuel and oil, so these fluids will float on top of the DEF.
• It has a slight ammonia smell.

If you suspect that the DEF has been contaminated but are unable to confirm by smell or color, you should test the fluid using a refractometer, or on some vehicles a DEF quality test can be run using a scan tool.