Oil Pressure gauge freaking out

if it fluctuates, you may be sucking air, but I doubt it. Air in the line generally dampens the needle swing. When you crack the fitting (in a rag) the needle usually tightens up and a little vibration is typical. if your really looking for the least amount of air, invert the gauge and drip oil into the sender hole until it overflows, then hook it to the line. fluttering over 20 psi is not normal. Try this, introduce a little air INTO the line and see if it dampens the needle any. Air is compressible but wont affect the reading. The good gauges have a damper in them, or so its said.