Duracool (and the stuff that Fox sells) is a formula derived from
Propane and Butane (and still contains the mercaptin aroma). When I
charge my system, I put enough to engage the low pressure switch
(around 35-40 psi on the low side.)

My experience is that it is just as effective as the R12 (and a whole
lot better than R134)

On May 25, 2005, at 11:57 AM, Vanagon wrote:

> They do say you HAVE to charge the system with LESS by 34 percent than
> the
> original R12. which I have heard is not really proper to do to an R12
> system
> and has its own set of drawbacks. Of course the makers of dura cool
> will
> CLAIM EVERYTHING is perfectly compatible and even colder than original
> R12
> set up. So do ALL the other replacement products. Truth  is only found
> out
> later by those in the KNOW that things are NOT always compatiable or
> proper.
> This has happened a lot already with all of these replacements.