What is def fluid made of?

DEF (Diesel Exhaust Fluid) is primarily a mixture of 32.5% high-purity urea and 67.5% deionized water. That's it. The purity of both components is critical for the proper functioning of the Selective Catalytic Reduction (SCR) system in diesel engines.

Here's a breakdown of why the purity is so important:

• Urea: The urea must be automotive-grade, highly pure, and free from contaminants that could clog or damage the SCR system. Impurities can lead to reduced effectiveness of the system and even damage to the catalyst.

• Deionized Water: The water used needs to be deionized (or very highly purified) to remove minerals and other impurities that could react with the urea or the SCR catalyst. Tap water, for example, is absolutely unsuitable due to its mineral content.

It's important to note that while the basic components are simple, the manufacturing process is tightly controlled to ensure the precise ratio and purity of the final product. Using anything other than certified DEF can severely damage the emission control system of a diesel vehicle.