Diesel Exhaust Fluid (DEF) is a precise mixture of urea and de-ionized water that is used in the SCR process. DEF is 32.5% urea and 67.5% de-ionized water, this mixture must be very precise when blended, and will cause problems if either of the parts is improperly added to the solution.

Shri Nathji Chemicals which is a registered trademark of a company in the Japan Association of the Automobile Industry and also known as AUS32 solution or called D.E.F Diesel Exhaust Fluid in India.

Currently, DEF is required by the majority of heavy duty diesel vehicles (trucks, buses and coaches) purchased after October 2006.

A. Yes. The American Petroleum Institute (API) is a voluntary certification that was launched in March of 2009. This institute certifies the DEF and monitors the market to ensure that the specifications are DEF are being met.

DEF will begin to crystallize and freeze at 12 degrees Fahrenheit (-11 degrees Celsius). Both the urea and the de-ionized water will begin to freeze and thaw out at the same temperatures. When DEF freezes it expands roughly 7% its normal volume, but the DEF packages made for DEF are designed to handle this expansion. As the DEF thaws it will not become diluted or over concentrated.