The EPA does not recognize any "drop in" replacements for R-12 meaning that there is nothing which you can use to "top off" the system if you have R-12 in it. You must remove all of the R-12 (capturing it to send for recycling) and replace with whatever susbstitute you choose. There are many substitutes but none will equal the capacity that R-12 can provide without major modifacations to the system. Many shops no longer have R-12 in stock because of the high cost ($60 a pound). Find a large shop or one that does classic cars, there are still some around, or call a supplier that the A/C contractors use (look in the phone book) and they can tell you who is still doing R-12 service work. You must be EPA certified to do R-12 work so many shops get around that by not using R-12 anymore. Be aware that some of the substitutes use propane or butane and are not to be used in mobile applications. Many of the substitutes are just blends of several different freons and as they leak the system will do funny things as the different freons tend to leak at different rates. The high side (head) pressures will also be higher causing the system to run hotter which deteriorates things like hoses and seals faster. The bottom line is after you do all of your homework the best option is to stay with R-12 for as long as you can. The only drawback to staying with R-12 is that it is a little more expensive to recharge with. David Teitelbaum vin 10757 --- In dmcnews@xxxx, "John L. Rahn" <john_rahn@xxxx> wrote: > Since freon is hard to find, does anyone have any experience with > the "so-called" direct freon replacements?