Another A/C Thread

[arew264]

Okay, I am a high school student and I get to drive an 84 300d to and from school for several years.

This car has been converted to R-134, and from what I'm reading here, this will not suit the purpose well as I will be driving very little over 30 mph.
It should be mentioned that I live south of Houston, Texas.

One alternative I have seen is Duracool. From their website, I see that they have a formula designed to replace R-134, but would it be as good as the R-12 replacement? Would any changes be necessary to use it?

I know the basic principals behind A/C and understand basically how it works in this car, but I am not experienced here. At all.