Any idea what the oil pressure should be for a 1998 5.7L motor? I'm running Mobil 1 5w30 and have about 22psi at idle anywhere from 40 to 50 as soon as I give it throttle. I'm at 115,000 miles and want to make sure nothing is going wrong...

That sounds about right. It sure is better than the 15-30 psi that I am getting when hot, in my 305, with 20w50.

There are a couple things to ask: 1) the oil pressure gauge is the electrical one on the dash; isn't it? 2) Have you changed out the oil pressure sending unit recently?

I have found on my 91 (remember I said 91---it m ay not be the same with your model) that the oil pressure indication was affected by the contacts in the dash plug for the electrical. I cleaned the contacts (after pulling the instrument panel) and the readings were changed on the gas and oil pressure gauges. I have also found that the oil pressuer sending units will read seriously different than any other unit. You cna change your readings by just putting in a different sending unit.

You might consider purchasing a cheap mechanical oil pressure gauge and c onnect it to see what the reading is and match it to your gauges on the dash, then you would know for sure.

I run 10W-30 oil with a friction reducer additive and I get about 28 psi at idle and up to 35 at higher RPMs. I have had readings on my gauges as low as 15 at idle, so I connected a mechanical and found the instruments on the dash were indicating wrong. I changed out and cleaned parts until I dfound a happy medium on my indication. My motor has 198,000 + miles on it.