I know I've seen a lot of posts about A/C problems, so I checked the archives but could not find an answer to my specific question. If I missed something in my archives search, I hope someone can properly point me in that direction. In the meantime, my question is as follows...

I took my '92 wagon to my very trustworthy and reputable mechanic to have, among other things, my A/C system tested (it hasn't worked in a while). It uses the old R12 refrigerant. My mechanic told me that no one in my town (I live in a small town) has the equipment to remove the old R12 still in the system, and that the only guy in town who could have done it hasn't done it in about 4 years. So, instead of converting the system to R134a, he recommended we use a product called R12a, which is hydrocarbon based and compatible with the existing R12 set up. Does anyone have experience with this product and is it advisable to use it? Is it environmentally friendly? The diagnosis on my system itself is that the compressor comes on, there just appears to be a small charge left. Anyway, thanks for your help.