NO!! Hot shot is a corktail soup. 53% R22 ( no way), 34% R12, 10% r143a, And here's the scary part, 3% R600a which is isobutane. Can you say melt down. I have retro fitted 100's of cars using R134a in my business. I will go with nothing else!! The posts are accurate as far as retrofitting to 134a. As far as the oil I use, its pag 150 vis. in GM cars. The mineral oil is not compatible with 134a.  I can still get r12, but you have to be careful where you get it. There's a lot of contaminated r12 coming across the border. If the repair is done properly with no leaks epically on older cars I use r12. That's what the older cars are designed for. The big reason is the hoses. The newer cars use a barrier hose, meaning its lined with teflon. R134 can absorb through the older style hose. I haven't really seen enough difference in the duct temp between the two. The big advantage of using 134a over r12 is the price. I'm paying around $100.00 for 30 lbs. of 134a as opposed to as much as $1200.00 for r12. I am charging just about as much to retrofit as to charge with r12, however if the ac needs to be charged again in the future it costs a whole lot less. If the repairs are done properly it shouldn't need to be charged again for a long time if ever. Just my opinion. Hope it helps. Terry

    As a rule if it's blowing good cold air your good to go!!  The system is supposed to be completely sealed so about the only maintenance is to keep the condenser clean and free of bugs and dirt.   If your getting good cold air after 3 years I would say your in good shape.  The more you run the system the better, does it no good to sit..  As the oil moves through the system it keeps all the seals lubricated and doing their job.

 

BTW Cold air is coming your way, it's creeping into Tennessee as I type!!

 

Mel