I have 2 refregerator compressors that I use quite a bit. One is set up with an automatic on/off (120 psi.) with an unloader valve, and a 1 gal. tank. The other I use for vaccume with a 20 lb freon tank as a reservor. I use my mighty vac or an airplane altimiter (threaded port on the back that goes to the static air vent) for guages. The altimiter gives you a much faster indication of what is happening when testing for a slow leak. They both have oil sumps in the bottom with sight guages. I had to add some compressor oil to one of them when I first got it. They have used virtualy no oil in 18 to 20 years. Besides being portable, I use the pressure one a lot plugged into my big air tank so I don't have to listen to my big compressor chugga-chugga.

Lou