Specifically designed for diesel engines, ACDelco Diesel Exhaust Fluid (DEF) is an aldehyde free, NOx (Nitrous Oxide) reducing treatment. ACDelco Diesel Exhaust Fluid is a stable, colorless, non-flammable, non-toxic primary component used to help convert NOx, an environmental pollutant, into harmless nitrogen and water. This product is a mixture of high purity synthetic urea and deionized water and is classified as minimum risk for transportation. ACDelco Diesel Exhaust Fluid meets the stringent ISO 22241 standard for purity and concentration, meets API regulations, and meets GM OE specifications.