Oil guage fluctuating

I have a 05 Jimmy, and yesterday I noticed my oil pressure guage would drop to about 1/4 when at idle, like sitting at a stop light, then back up to half or so when driving. Is this normal? I haven't had the vehicle for very long and I don't think it has done this before. Should the guage be staying at one pressure the entire time my engine is running?

I have a 05 Jimmy, and yesterday I noticed my oil pressure guage would drop to about 1/4 when at idle, like sitting at a stop light, then back up to half or so when driving. Is this normal? I haven't had the vehicle for very long and I don't think it has done this before. Should the guage be staying at one pressure the entire time my engine is running?

Completely normal.

The oil pump is hooked in with the distributor.

More rpms = more flow and pressure.