The air and a short sweep 100lb gauge can give you quite a bit of varience in reading from the actual pounds of pressure.
Found out a long time ago I wanted a LOT of movement in my needle so I could get a good reading of the pressure.
However most new OEM oil pressure gauges go to the middle after 7 or 8 pounds is seen and stay there until the pressure gets below them numbers...thay really don't READ the actual pressure. They act the same as a red light would act..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

professional bovine relocation specialist