Oil pressure guage shows little to no pressure at start up

[Bonneville'sRock]

Greetings! I have an 2000 SLE. My son drives this car and he's been away for awhile. When I started the car yesterday I notice the oil pressure gauge was at zero...it eventually move just outside the red...no bells were on and no motor noise, I shut car off quickly. My wife drove it earlier yesterday and said it ran fine. I noticed the oil/lube place he took it took put in 5w30. Any thoughts? The gauge sweeps upon start up. Update...just went out and started car....oil pressure started at zero and after about 5 min. of idling gauge slowly moved to 40 PSI on gauge. Shut off car and repeated...same.... starting at zero and moving up to 40 PSI on gauge. motor sounds fine. Thoughts?

[Bugsi]

Possible bad oil pressure sending unit. If you replace it, I recommend getting an AC Delco from a dealer rather than an aftermarket. I've had aftermarket ones give strange readings, where AC Delco ones are spot on.

[rustyroger]

X2 on using genuine parts.
5w30 oil is what the makers recommend.I would add use a reputable fully synthetic brand.

If the car had the (lack of) oil pressure the gauge indicated it wouldn't get far......

Roger.