Clean Diesel Engines Use DEF

DEF is injected into the exhaust of diesel engines from a separate on-board container to reduce NOx emissions in a process referred to as selective catalytic reduction (SCR). In addition to all on-highway vehicles, these applications are among those that require SCR-equipped diesel engines according to federal emissions standards in the United States:

Storing DEF for dispensing requires special care. DEF is a solution made of high purity urea and deionized water. It is non-toxic and safe to handle. But DEF can corrode some metals and needs to be stored in a manner to keep temperatures between 12°F and 86°F.