Diesel Exhaust Fluid (DEF) is an operating fluid for Selective Catalytic Reduction (SCR) technology, which will be in new heavy duty commercial vehicles from 2010. DEF is not a fuel or fuel additive; it is injected into the exhaust system to chemically reduce NOx emissions from diesel powered vehicles. DEF is a high-purity urea solution complying with the Standards of ISO 22241. This is the highest quality and safety standard in place which ensures the correct functioning of Selective Catalytic Reduction equipment. Most engine manufacturers chose SCR over competing technologies due to the fuel economy benefits of SCR as compared with other options. SCR is expected to improve overall fuel economy by approximately 5%.