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So, my oil pressure gauge used to go from 60+ at warm up to 40 as I drove down the road. Then, months later, it stayed 60+ at warm up but dropped to 30 on the road. Just today, I noticed it dropped down to 15 on the road. I checked the oil. It was fine, The whole engine had a complete rebuild 10,000 miles ago, and the cuno oil filter is NOS from John at Midwest Military.
I noticed when I was accelerating, the oil pressure was up at 50-60, but would drop back down at idle at traffic lights. To as low as 10 now. The really strange thing, is that at warm up, it is at 60. After warm up, it is still 60, until I ride it around a bit. How can I test the sender without removing it when I think it is misreading, but that is only when the engine is hot, and only after I have driven it around?

Mine does that too. It's never been a problem. An old guy once said worry more about high oil pressure,then low - with high passages are clogged, something isn't getting oil

I'm assuming you have the standard electrical gauge in your instrument panel. Buy a direct reading oil pressure gauge, the kind that is plumbed into the block. There are several ports on the left side of the engine where you can access the oil gallery there. Thread the oil line into the passenger compartment and temporarily mount the gauge where you can read it - duct tape, baling wire, etc. - it won't be there long. Compare readings between the electrical gauge and the temp pressure gauge while driving around. If the readings are the same you know your original gauge is fine. If they are different, you can troubleshoot your sender and gauge using the Troubleshooting Guide for 24 Volt Gauges found in the Downloads section of this website. However, 10-15 psi at idle for a warmed up engine doesn't sound to far out of whack to me.

I have a separate gauge I can screw into the block. The issue is, the lower oil pressure readings only pop up if I take the vehicle out for a drive that is more than 15 minutes. Otherwise, they seem to be what I am normally used to. I guess I could do that with the separate meter screwed in and taped to the firewall. I'll just have to take local roads and drive around for a few.

my new rebuilt engine has about 150 miles on it(don't drive it much). my oil pressure at start up is around 50 and maybe higher, once warmed up and driving it drop to about 15-20. ive always been told that's normal

Ok, it does make me wonder why it was 40 at idle for so long though. The sender and gauge were both replaced when the engine was rebuilt. The sender from John at Midwest military and the gauge from Rapco. The engine runs great. I have Shell Rotella SAE 30 in it. And I change the oil frequently. Like every 3,000 miles.

I would think if there was a blockage in the cuno filter it would read high, not low. I changed the oil, and rotated the cuno oil filter handle a bunch of times., and now it never gets below 20 in the oil pressure gauge. Before it was dropping down to 10.