How Long Does A Bottle Of Diesel Exhaust Fluid (def) Last Once Opened?

Eblis/Getty Images

We whitethorn person a committee connected purchases made from links.

The government's strict emissions limits for combustion-powered vehicles person pushed automakers to create technologies that fto their engines enactment compliant while producing gobs of power. Diesel exhaust fluid (DEF) is 1 important component, designed to trim diesel engines' nitrogen oxide emissions. Sometimes known arsenic AdBlue, DEF is simply a solution of deionized h2o and urea, stored successful a abstracted vessel from nan substance and automatically sprayed after combustion into nan engine's exhaust stream.

There, DEF turns into ammonia and isocyanic acid, which respond chemically pinch exhaust gases for illustration nitrous oxide and break them down into harmless substances specified arsenic nitrogen, h2o vapor, and c dioxide. The capacity of your DEF vessel varies based connected your vehicle but typically ranges from 5 to 25 gallons. The vessel must beryllium refilled from clip to time, arsenic vehicles use a gallon of DEF for each 50 gallons of diesel substance burned.

While you tin find DEF astatine immoderate state stations, it's often sold successful containers astatine motortruck stops, which aren't recovered everywhere. So drivers often bargain an other jug and shop it for erstwhile they whitethorn request it and find it retired of reach. Unopened DEF typically lasts astir 2 years from erstwhile it was made earlier it goes bad. But erstwhile you've opened it and person an excess, it's expected to past astir a twelvemonth sitting successful nan vessel earlier it breaks down, provided it's stored properly: sealed and successful a cool, barren spot distant from sunlight (ideally betwixt 12 and 86 degrees).

Simona Jurasova/Shutterstock

While DEF is created for agelong support life, letting it beryllium for galore months earlier utilizing it whitethorn not beryllium nan champion choice, arsenic improper sealing aliases important headspace successful nan jug tin origin it to evaporate and crystallize. But you tin show if your DEF has gone bad conscionable by looking astatine it, since contaminated DEF looks cloudy, discolored, aliases crystallized alternatively of clear, aliases beryllium heavy alternatively than easy-flowing.

This is your cue to dispose of nan aged DEF. And being truthful reasonably priced — you tin get 2.5 gallons of BlueDEF for astir $21 — it won't wounded to ever usage a caller 1 alternatively than settee for aged fluid, which mightiness beryllium little effective and moreover harm your selective catalytic simplification system. The bully point is that your conveyance will show a informing ray to punctual you to refill nan DEF vessel good earlier it runs out. This reduces nan likelihood of being caught disconnected defender and eliminates nan request to transportation an opened vessel of DEF around. 

However, if you're redeeming already-opened DEF for early use, make judge nan headdress is securely tightened to forestall it from mixing pinch aerial aliases different pollutants for illustration dust. And debar storing it adjacent nan motor aliases exhaust to forestall degradation from power exposure. Then again, each this assumes you're keeping your emissions systems intact, and aren't considering deleting your diesel truck.