If you put Freeze12, or any of "drop-in substitute refrigerants" in your vehicle, plan on servicing it yourself. We won't touch it.
Cross-contaminated (mixed) refrigerants cause enormous problems in the mobile a/c industry. You have to have dedicated equipment for each refrigerant used; store each recovered refrigerant in a seperate, labelled DOT container; have to account to the EPA every year what refrigerant & how much is inventoried; I can go on from there.
The EPA deems me liable for even accidental cross-contamination. A truck comes in our shop with a drop-in in it, and we recover & recycle from it, I'm monetarily liable for every car that machine services from then on, and every recovery machine that services that car from then on, and every a/c unit THAT recovery machine services from then on...
your truck is not worth a million dollars in liabilty.
But the best part? The vehicle OWNER who put the goofy-arsed "blend" refrigerant in it... is NOT liable...
So I don't give a damn what the EPA tells you, the EPA tells me different.
Use Freeze12 at your own risk.
--edit--
From Bush's link..
Are flammable refrigerants automatically unacceptable?
EPA considers flammability as one factor in the SNAP risk screen. Rather than serving to disqualify a substitute, flammability may necessitate additional testing and assessment of risk. The risks from using a flammable refrigerant, such as a hydrocarbon, are extremely dependent on the conditions and type of equipment. EPA believes that it may well be possible to safely use flammable refrigerants, and encourages manufacturers to contact SNAP to discuss the information needed to support such a submission. To date, hydrocarbons have only been found acceptable in industrial process refrigeration. It is illegal to use hydrocarbon refrigerants as CFC or HCFC substitutes in motor vehicle air conditioning. Furthermore, only a few hydrocarbon blends have been evaluated for other end uses, and those (HC-12a®, OZ-12a® and Duracool 12a) have been found unacceptable in all refrigeration and air conditioning end uses other than industrial process refrigeration. A fact sheet provides information about HC-12a®, OZ-12®, and Duracool12a. These refrigerants, as well as propane, butane, isobutane and propylene, have been found acceptable for industrial process refrigeration.