Diesel Exhaust Fluid (DEF) is a liquid used to reduce the amount of air pollution created by a diesel engine. Specifically, DEF is an aqueous urea solution made with 32.5% urea and 67.5% deionized water. DEF is consumed in a selective catalytic reduction (SCR) that lowers the concentration of nitrogen oxides (NOx) in the diesel exhaust emissions from a diesel engine. DEF is a requirement for medium- and heavy-duty vehicles with diesel engines produced after 2010. DEF is not a fuel additive and is stored in separate tanks. DEF is made up of deionized water and urea, which help turn nitrous oxide, a harmful type of emission from diesel engines, into water and nitrogen, two everyday substances that make up the air we breathe. DEF is offered to consumers in a variety of quantities ranging from containers for single or repeated small usage, up to bulk carriers for consumers requiring a large amount of DEF. DEF can be purchased in several ways, including through fueling dispensers when equipped. DEF is a great product for all c-stores to offer since there is a large population of vehicles on the road.