Larry's probably thinking of OZ-12, which is/was a hydrocarbon (i.e propane/iso-butane mixture) which
replaces R-12.

Some of the blends appear to cool better even than R-12,
which should be interesting to those of us with old,
marginal a/c systems. Here's some websites at which to
fritter away your time:

The Autofrost site. This is the blend invented by George
Goble. George is mostly noted for "accelerating" his
BBQ grill by pouring a bucket of liquid oxygen over the
coals.

http://www.autofrost.com

The air conditioning alternative refrigerants message
board:

http://www.aircondition.com/wwwboard/alternative/

And last, but not least, the dreaded Cryo-Chem website!

http://www.cryochem.com/