R-140b refrigerant
 

Anyone have experience in using this as an alternative to R-12 or R-134 in any MB...like a '91 300e??

I think it is primarily used a refrigerant for refrigerated truck use.

I'm not taking the time to look up this particular refrigerant, but I'm quite sure that it is either a blend or an HC(flammable).

Blends are problematic because if you have a leak, the elements leak at different rates requiring complete recovery, evacuation and recharge after any repair.

HC's are illegal in 18 states.

EITHER TYPE will contaminate any recycled refrigerant that they are recovered into. This could spoil as much as 50 pounds of good refrigerant if added to the cylinder. You will find no shop that will recover it or work on the a/c if it is in the system.

Your system was designed for R12. R12 is coming down in price due to decreasing demand. Do yourself a favor, fix the leak or whatever problem that has led to your needing to recharge and then recharge with R12. Don't mess with these Snake Oil alternative refrigerants. You will be doing yourself a HUGE favor.

Good luck,

I'm not aware of r-140b. Not listed in the usual places.

There is a 410b, but that is high-pressure (not automotive), and still in R&D.

Refrigerated Trailers/Trucks
 

404 and 502 in our refrigerated equipment. - and would not be a (wise) choice for our little compressors.