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What is Diesel Exhaust Fluid?

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Diesel Exhaust Fluid (DEF), also known as AdBlue®, is a solution used in modern diesel engines equipped with Selective Catalytic Reduction (SCR) technology. It is a clear, non-toxic, and safe-to-handle liquid primarily composed of 32.5% high-purity urea and 67.5% deionized water.

DEF plays a crucial role in reducing harmful emissions from diesel engines, specifically the nitrogen oxides (NOx) produced during combustion. When injected into the exhaust stream, DEF undergoes a chemical reaction with the NOx in the presence of a catalyst, converting them into harmless nitrogen gas (N2) and water vapor (H2O). This process is known as selective catalytic reduction.

To use DEF, a separate storage tank is installed in diesel vehicles, usually near the diesel fuel tank. The DEF tank has a dedicated fill port, and the fluid is dispensed into the tank using a specialized nozzle. The amount of DEF used depends on the engine’s NOx emissions and is typically consumed at a rate of 2-4% of diesel fuel consumption.

It’s important to note that DEF is not a fuel additive, and it should never be mixed with diesel fuel. It must be used in the designated DEF system to ensure proper operation of the SCR system and compliance with emission standards. Additionally, DEF has a limited shelf life and can freeze at temperatures below 12°F (-11°C), so it’s necessary to store and handle it appropriately to maintain its effectiveness.

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