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Is diesel exhaust fluid necessary?

Yes, diesel exhaust fluid (DEF) is necessary for specific modern diesel engines with selective catalytic reduction (SCR) systems. DEF is a solution of urea and deionized water injected into diesel engines' exhaust stream. It plays a crucial role in reducing nitrogen oxide (NOx) emissions, which are harmful pollutants.

In the SCR process, DEF is sprayed into the exhaust gases before they enter the catalytic converter. The heat from the exhaust causes the DEF to break down into ammonia, which then reacts with the NOx emissions, converting them into nitrogen and water vapor. This chemical reaction helps to reduce the harmful emissions produced by diesel engines.

Vehicles with SCR technology typically have a separate DEF tank, and the system monitors the DEF level to ensure proper operation. If the DEF tank runs low, the vehicle may enter a reduced power or "limp" mode until the DEF is replenished. Therefore, it is essential for owners of diesel vehicles with SCR systems to regularly check and maintain an adequate supply of DEF to ensure compliance with emissions standards and proper engine performance.

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