what is the correct oil pressure for a small block

[kikkegek]

I have been driving my Burb for about 4 months now. I noticed that the needle for the oil pressure is at about 15-20 (in the middle of 0 and 30) all the time.

So after a cold start, running idle, running 55 mph and when the engine is warmed up, the needle always seems to be in the same place.

so three questions:

1. is 15-20 OK? (is this psi of mbar or what?)

2. shouldn't the needle move when increasing rpm's?

3. should there be a difference in cold and warm oil pressure?