Vacuum can also be expressed in psi. Or also in mm-Hg. 15 in-Hg (380 mm-Hg) is equivalent to about 8 psi, a far cry from 100 psi that the freon system runs at.

 

Bought a 12 oz can of refrigerant. My friend has a hose w. pressure gauge. The pressure was just a little under the "V".
Emptied the whole can, but didn't really see any significant change in pressure.
Will leave it and see how it works on a longer ride.
Thank you all for the replies. Will keep you posted.