Oil pressure dash light, (low oil pressure), stays on longer than other warning lights after starting. Oil pressure gage stays within normal range. Oil level is good. It happens on level ground and incline. Didn't find anything in the OM about it. Just wondering if it's anything that needs to be checked out.

 

What's your hot oil pressure at idle after a freeway run? And what PSI are you running going down the freeway?

As far as the oil pressure light going off when you start it, it will take a second or two to build up pressure. If it's taking 5 seconds, I would suspect the oil pick up tube o-ring.

The simple test for that is overfill your crankcase by two quarts, either jack up the rear end or point it nose down on a steep hill and start it. If the oil pressure light goes off noticeably sooner, that's your problem most likely.

If there's no change, I would start by replacing the oil pressure sending unit with a genuine GM AC Delco unit. (While you have the old one out.... Get yourself a sending unit relocation kit, so you can zip tie the sending unit up against the firewall. Been temporarily hook up a mechanical oil pressure gauge to verify everything before putting the new one on.

Other possible issues can be a weak oil pressure relief valve in the oil pump. Or it's full of crud. Or a bearing issue bleeding off enough pressure it takes a couple seconds longer for the oil pump to be able to build up enough pressure. Usually that's the front cam bearing.

 

How many miles? Model year? 6.0 or 6.2?

 

Hey RD, thanks for the feedback, it's a 2005 H2 SUT, 172150 mi and a 6.0. Initial start-up is 30, Hwy 40. Idle after Hwy 20. Take off after Hwy is 40. Of course, the oil low-pressure light must have heard I was talking about it and decided not to stay on today. My guess is the previous times, the OLPL stayed on 2 sec or less.

 

30 on a cold start is somewhat lower than I would expect. So is 20 at a hot idle. At that mileage, the o-ring is probably past due to be changed on the pickup tube. I would change out the oil pressure sending unit first though. My 6.0 is the 2003 model. 50 to 55 PSI cold start. 38 PSI at a hot idle after a freeway run. Cruising on the freeway is about 55 PSI at 1800 RPM. The 6.0 is a very solid engine for a lot more miles than you have on it. The o-ring on the pickup tube is pretty much a maintenance item, the OEM oil pressure sending units are known issues. At that mileage I'd be tempted to drop in a Melling 10296 oil pump that comes with the +10 PSI pressure relief spring installed. (It's quite possible you might have some debris in the oil pressure relief valve in your current pump. If you pull off the front cover to deal with that, you might as well just replace the pump)

I would recommend against following the oil life monitor for your oil changes. Full synthetic 5W30, no more than every 4,500 miles.... And it will run a long time.

 

A side note. Disconnect your PCV hose and make sure it's not plugged. If it gets plugged, you'll build a lot of condensation in the bottom of the crankcase affecting your oil pressure. You'll know if you pulled the drain plug in the first thing that comes out is white or beige....

 

Good info, I like to be informed when talking to my mechanic.

 

Do an oil change. Use the oem spec acdelco filter with anti-drainback valve and see what it does.

 

Everybody has their favorite oil filter these days.... mine is the AC Delco UPF46R.

No plastic parts inside to get brittle and crack, better quality construction in the UPF series.

 

Ill keep that in mind. I usually run a pf48 or the mobile 1 equivalent. I actually think I like the mobile 1 better. Metal inside and usually free with the bundle deal. Looks like a wix with better quality control.