let us know how the propane/butane mix works. I have been thinking about use that when I run out of r12. Some people told me they would be afraid of using a propane/butane mix as it is flamable. But so is r12 and r12 puts of leathal gas when burned.
I am not sure but I think most R12 replacements like jonsens freeze 12 is a propane/butane mix. I really do not want to do a 134a conversion as they never worked well.

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1986 560 SEL
1960 Ranchero
1970 Cougar XR7
2002 Crown Vic Sport
1992 F150