DEF is a chemical solution comprised of 32.5 percent automotive grade urea and 67.5 percent de-ionized water. A naturally occurring compound made up of ammonia and carbon dioxide, urea is colorless, odorless, non-hazardous, non-flammable and non-combustible. It is used in a variety of industries, including as a fertilizer in agriculture.
Average DEF consumption may range from 2 to 4 percent per gallon of diesel fuel burned. However, results will vary by engine make and model and vehicle operation and application.
Automotive grade DEF must meet stringent purity standards. The American Petroleum Institute (API) has a certification program that allows DEF manufacturers and marketers who meet consistently meet the quality and performance standards set by the International Organization for Standardization to use the API Diesel Exhaust Fluid Certification mark.