Well, I am an AC expert. I hold EPA 608 universal certification along with 609 MVAC. 608 universal requires real study and testing unlike the 609 they hand out to anyone for $20 and an open book test on the internet. I can work on anything from a car to 200 ton roof top units. You on the other hand don't know what you don't know so I'm going to explain it. Follow along here: Freeze 12 is an alternative refrigerant that's been approved by the EPA for some time. The problem with it is a case of pay now or pay lots later.
The reason the so called quick change 134 "death kits" sold in auto stores are bad is because they cheat on the oil. MIneral oil used for 12 is not miscible in 134 therefore it will not circulate with the refrigerant. The entire point of doing a proper conversion to 134 is to remove the mineral oil and replace it with PAG or POE, the two oils that *are* miscible with 134.
So what? The compressor is lubricated by oil. The oil circulates with the refrigerant. If it doesn't the compressor will seize. When it does it sends chunks of itself throughout the system. It's called Black Death in the MVAC biz. When it happens at minimum a new pump, receiver/dryer and complete system flush is needed. Usually the expansion valve and condenser must also be replaced because they can't be cleaned. Expansion valve replacement on this car requires evaporator removal. The cost can really add up.
Freeze 12 is 80% 134 and 20% R142. The reason it can be "dropped in" a CFC-12 system without changing to PAG or POE oil is because mineral oil *is* miscible in 142. But in a Freeze 12 system instead of 100% of the refrigerant carrying the oil it's now only 20%. To make matters worse 142 is a smaller molecule compared to 134, which is smaller than CFC 12. Since the MKIII didn't come with the barrier hoses required for 134 systems Freeze 12 will leak. Hell, all MVAC systems leak becuase of the use of flexible hoses and lack of hard plumbed connections as used in stationary systems.
Anyway, the 142 will leak. Since it's the only thing in Freeze 12 that's capable of carrying the mineral oil that was left in the system it'll take the oil with it. Even if it leaves the oil behind they'll be nothing left to circulate it. And remember, it's only 20% of the mixture. Guess what happens when it's gone? Boom. The user gets to rebuild his entire system at a cost of a thousand bucks or more. Notice how the low pressure cut out switch fails to protect against this since 80% of the refrigerant remains. Nor can you top up Freeze 12 since an azeotropic mixture.
Now I ask you, since the stuff is 80% 134 in the first place does it makes sense to use it rather than properly convert to 100% 134 with PAG or POE? A case where 100% of the refrigerant is carrying the oil and when it leaks no harm will come? With Freeze 12 it's just a matter of time but they never tell you that. Trust me, your time is coming. 4-5 years is typical. Better start saving now.
It's just another example of cheap and clueless people who don't do things right and later come back to whine when it bites. The Supra community is filled with them. It really does get old. Btw, that website is pure BS. There is no shortage of CFC-12. The prices have even come down recently. I've got 90 pounds of the stuff just lying around.