Interesting thread - nothing like R12 vs R134a to get the opinions flowing.

Until very recently, I bit the bullet and used R12 for my four cars that need it. Yes, I'm certified to purchase R12.

However, it is illegal to sell R12 in anything less than the large cylinders that the 609 license does NOT cover in Wisconsin. A 30lb cylinder is now running $1000. R12 is scheduled to be illegal to sell after the end of this calendar year in the US, I've been told.

So, my decision is to go ahead and convert to 134a when faced with the next major A/C service or if recharge is needed. In the long run, it makes the most economic sense.