This oil-pressure thing is subtle. Oil pressure is variable with engine temperature, engine age, oil specification, oil age, oil-change frequency, oil additive, ambient temperature, bearing condition, sensor accuracy and your zip code, birth date and shoe size. You think I'm kidding about the last two, but I'm not. Your driving style affects oil pressure.
The analog pressure gauge gives you lots of information about the general condition of your engine; how it's performing under load and if something serious is happening (or about to happen) with the crankshaft bearings.
If you divide the total square-inch area of the crank bearings by the indicated oil pressure, you get a picture of how well the motor is lubricated under load. Ideally, there should be absolutely no friction between the crank and the connecting rods, thus the perfect lubricant: Liquid Rock (petroleum). As wear-and-tear gradually increase the space between the moving parts of your engine, absolute oil pressure decreases. But it does not decrease absolutely; temperature affects viscosity and suspended solids and dissolved byproducts of combustion affect the capability of your oil to lubricate.
Change your oil frequently. Acid buildup deteriorates your engine's bearing surfaces and carbon abrades those polished surfaces your bearings need to slip and slide smoothly and silently. Change your oil frequently. The marketing machines say 4000-miles...I say twice a month regardless..like every other tank of gas. I'm not here to sell oil, but my '89 Cherokee 4.0 6-inline runs better every year and is a legacy item for my grandson.
Every once-in-a-while, unscrew the pressure sender and start the motor for about five seconds. What will happen is that oil will blast out of the motor all over your garage floor, but all the crud and debris in the oil pan will come with it. Get clever and you can do it without making a mess.
If the pressure gauge is flinging itself from left-to-right with wild abandon, it's probably an electrical problem. The wiring in the Jeep is fragile; connectors come unseated, insulation wears, wires break, etc. Troubleshooting electrics is a *****, but it's good to learn how to do it because your local mechanic can't invest the time to do it for you and make a profit on the work involved. Get-down!, bro..and learn.
The instrument cluster seldom (if ever) fails. It's just too basic. If your oil pressure is fluctuating and you're getting nervous, it's either the sender, the wiring, or dirt/debris in the veins and arteries of your motor. Marvel Mystery Oil is an excellent medication for clogged oil passages, but be prepared to change your oil and filter as you apply the cure because all the stuff clogging-up the system will come loose and has to be removed.
Change your oil.
Change your oil.
Do it again.
"Everyone is entitled to his own opinion, but not to his own facts."
1989 Cherokee XJ