One last thing....if the DEF is really just urea and water, then it is an EXCELLENT skin softener. I work in the dermatology field and we use 30-50% creams and lotions for thick skin. It is great in one of those sonic bath contraptions. You put a gallon in and heat it a little (like hot tub temp), and then immerse your feet for 20 min. It softens dry skin by bonding water. It also has some other interesting properties:
-antibacterial - it will kill bacteria rapidly on contact
-antifungal - it will kill this too, but if you have the fungus under your toe nails, it takes time.
-deoderant - if you have smelly feet, this will cure them if you soak regularly.
I know it sounds weird that a chemical you are using in your truck can be used medicinally, but it is totally true! Here is a link with more on urea:
and below is an excerpt from that.
Medical researchers have also proven that urea is one of the best and only medically proven, effective skin moisturisers in the world. In many years of laboratory studies, researchers discovered that, unlike just about all other types of oil-based moisturisers that simply sit on the top layers of the skin and do nothing to improve water retention within skin cells (which gives skin its elasticity and wrinkle-free appearance), urea actually increases the water-binding capacity of the skin by opening skin layers for hydrogen bonding, which then attracts moisture to dry skin cells.
Now, I'm not saying to go and use DEF for skin disorders.....but you could, and it would work! (assuming no other ingredients are in there but water and urea). My main point here is that DEF is a very natural product, not a dangerous chemical or something mysterious.