I'm the original owner of a '97 1500 with the 5.9 (360). Its got 175,000 miles and has had oil changes every 3000 miles and has been really well cared for. I have noticed over the last couple months that my oil pressure fluctuates quite a bit now. For the first 165,000 miles, my guage stayed in exactly the middle of the normal range regardless of rpm, temperature, etc. It never moved. Now it is only in that sweet spot when I'm cruising on the highway or after a cold start. At a warm idle the needle is barely in the normal range. It really moves with the tach quite a bit now.
What do you guys figure? Just replace a sending unit, or is my engine living on borrowed time and I should sell the odl girl? Other than this it still runs perfect.

 

depends on how much you like the truck. if you're tired of it and ready to move on, then move on.

otherwise, start with the cheapest things first.
1. do a couple of engine flushes with Gunk brand flush for about $5 each. follow the directions. it might unclog something or clean off the pickup screen.
2. try thicker oil. 20w50. maybe try different oil filter too.
3. replace the sending unit. about $25-30.
4. drop the pan and replace the oil pump, clean pickup screen and tube.
5. ignore it and keep driving.
6. ? rebuild it.

i've done all these, and it didn't make any difference at all. i run a little over halfway when cold. close to half at rpm, and a little under at idle. i'm at step 5... ignore it.

 

I have an 01 2500 quad cab 5.9l. My truck has done the exact thing your talking about since about 60,000 miles. I now have 187,000 miles and still no problems. As long as it's running normal when your moving I don't think it's an issue. If you even notice it running low while driving however, change your oil right away and it will return to normal.