Re: Peak Blue DEF - Walmart
DEF contains urea, very different from acetic acid which is vinegar.
Heat causes chemical breakdown of urea into ammonia. This is part of the process of how it works for selective catalyst reduction (SCR) in this system. The heat from the exhaust turns the urea into ammonia (thermal decomposition) which is the functional chemical in the reduction process. Heat in your garage or DEF tank if your GC is out in the heat for that matter does the same thing just at a much slower rate than when it's injected into the hot exhaust.