Your refrigeration guy is a moron. Freeze-12 does not contain any hydrocarbons and is not explosive. On the other hand, HotShot contains isobutane, which is explosive. The small amount of isobutane, in my opinion, doesn't justify worrying about it but it exists none the less. I'm not sure what you are doing, but if I were putting together a new A/C system from scratch, I would use 134a (like every new auto A/C system manufactured today... how can all the car manufacturers be wrong)? If I were trying to reuse some or all of my r-12 components, I would use freeze-12.

In my girlfriend's '89 740 it has a new condensor, receiver, and compressor with r-134a for 2 years now and still works great, vent temp in the mid 40's on a 90+ degree day.

In my '89 740 I used all the original r-12 parts and recharged with freeze-12 and it is working great, vent temp in the low 40's on a 90+ degree day. I can't comment on longevity yet since I did this only 3 months ago.

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Matt L. -- Cary, NC -- '89 740 sedan -- '91 740 wagon