It comes up now and then to purge air out of the oil sender line. When I installed my senders on the top corner of the motor mount by the firewall, I did not purge the air out of the line. The Van's gauge has worked flawlessly. Later when I added a second sender to the MGL, there was no oil in the existing fitting and no mess.
My point is, pressure is pressure. It doesn't matter if it is water, air, oil, propane in a liquid or gas state. Your oil pressure will compress the trapped air to the point of the pressure value placed on the oil, no more, no less. In fact, the trapped air gives a cushion to the gauge which may prolong it's service life.
My point is, pressure is pressure. It doesn't matter if it is water, air, oil, propane in a liquid or gas state. Your oil pressure will compress the trapped air to the point of the pressure value placed on the oil, no more, no less. In fact, the trapped air gives a cushion to the gauge which may prolong it's service life.