Freeze 12, Dracool, or Red Tek all operate at much lower head pressures
than the 134.

And  because of their molecular structure have less tendency to permeate
through the old rubber AC hoses and fittings.

I use the Red Tek alternative freon and am getting 38 degree's blowing
out of my vent's all the time, and has remained in the system for 3
years now without any leaking or compressor failure due to higher
operating pressure.

I'm very happy with it's performance, initial cost, and longevity in my
Van.

It's as good as, if not better than R-12.