I have a 2005 2500HD with a 6.0 and 228,000 miles. Oil changed religiuously by Chevrolet every 3000 to 3500 miles. When I first start it in the morning the oil pressure drops to 0 but goes back up to 40+ pounds upon driving. This fluctuation continues for 10 to 15 minutes and it is fine all day after that. I'm not sure if it is a sending unit issue, a pickup tube issue, or an oil pump issue. Any thoughts?

Does the idiot light ever come on?

At 228,000 miles, if it isn't making bad noises while showing low oil pressure and if it hasn't had the oil pressure sender replaced I'd replace it. See if that solves it.

A check engine light does not come on. The message bar on the dash says "Low Oil Pressure" and the alarm chime rings. The message disappears and the alarm chime stops after the truck moves about 20 feet. They only reappear at idle during the next 10 to 15 minutes and after that the truck maintains 40+ pounds of pressure all day.

Thanks. I'll give that a try. It'* certainly the easiest and least expensive

Can also try over filling the crank case by about 1.5 qts. this puts the oil level above the oil pump pick up o-ring that sometimes will leak and suck air. Just something else to try. Remember to drain excess oil when done as not to aerate the oil.

Not a good idea to overfill by a quart and half.

Never heard of anyone doing that before. I wouldn't do it. My $0.02

Thank you. I like the idea in principle but I want to give it some more thought because of the concerns of over-filling. I will check to see at what point over-fill will cause a problem,especially on a high-mileage motor.

That'* my concern too.