oil pressure ?

I have a 05 Chevy tahoe with 5.3 v8. I have recently noticed the oil pressure gauge. When I start up the pressure is around 40. Then it drops down to something like 30. When at high speeds it looks to be normal. Also at a red light while in gear it goes down to about 30. If any on can help I would highly appreciate the info.

Possibly the oil pressure sensor. However, check and double check your oil level first.

It is normal for it to drop between 30-40 when your idling and have been running around all day long though.