coolant pressure- is this normal?

[92EcoDiesel Jetta]

I Tee-ed in a pressure gauge as shown. Pic shows approx 3 psi (gauge with no pressure reads 2 psi) 48 hours after driving for an hour. At full hot, gauge reads, 17 psi, never higher. When at idle and the fan comes on, the psi will drop 3 to 5 psi. Is this residual pressure normal? Should coolant level in the expansion tank stay put or is it normal to lose some and have to top up? If so, how much is normal?

[Vincent Waldon]

15 - 20 psi (depending on your altitude, ambient temps etc) is normal... anything lower suggests a leak, anything higher suggests a overheating problem or possible headgasket/cracked block. The fact that it's holding residual pressure 48 hours after is a good sign of a nice tight system.

I believe the cap vents at 25ish psi iirc.