Diesel Exhaust Fluid (DEF) plays an important role in moderating truck emissions and meeting EPA guidelines. As with any type of vehicle fluid, regular monitoring of DEF levels is an important part of ongoing maintenance. While checking diesel exhaust fluid levels isn’t a difficult job, there are factors that can complicate the issue.

How Long Does Diesel Exhaust Fluid (DEF) Last? Diesel exhaust fluid normally has a shelf life of about two years. However, exposure to sunlight or sustained high temperatures can compromise it. Any DEF purchased at a truck stop or auto parts store will have a clearly labeled expiry date — using DEF past this