It has 190k miles and drives great. on a 2000-mile round trip
to whilster, BC I noticed that after a few hour of constant speed
highway(~70mph) the oil pressure guage starts to vibrate a little.
Then it starts to go beyond 60, 65, 70, 75, and eventually 80!
After a bathroom break, the guage is normal initially, but goes
all over again in a an hour or two. Slow speed has normal reading(~45-50). But not at highway speed.

I want to make a jeep record for a quarter-million miles. Anyone
know what the symptom is? any similar experience to share would
be great.

Nothing but routine oil change and good driving style(ski trips
mostly). So proud of jeep that I will get another one later.

It's either the gauge, sender or an internal problem.
Clean up the oil pressure sender, wire and contact. Degrease it and use a bit of sandpaper to buff the electrical contact.

If the problem persists, Try installing an aftermarket mechanical gauge, to varify the proble. If the problem persists, and is internal, most likely its a jammed or dirty pressure relief valve on the oil pump. Remove the pan, and pump. As the engine is high mileage, install a new pump, its probably well worn anyways.
If the pressure gets too high, it will blow the oil filter off, and dump all the engine oil on the ground.

It has 190k miles and drives great. on a 2000-mile round trip
to whilster, BC I noticed that after a few hour of constant speed
highway(~70mph) the oil pressure guage starts to vibrate a little.
Then it starts to go beyond 60, 65, 70, 75, and eventually 80!
After a bathroom break, the guage is normal initially, but goes
all over again in a an hour or two. Slow speed has normal reading(~45-50). But not at highway speed.

I want to make a jeep record for a quarter-million miles. Anyone
know what the symptom is? any similar experience to share would
be great.

Nothing but routine oil change and good driving style(ski trips
mostly). So proud of jeep that I will get another one later.
:nono: IF YOU EMAIL ME DIRECT AT jeepman600@aol.com I'll send a article on checking out your oil pressure & gauge--jeepman600@aol.com
These are my files & i can't send thru forum DALE
:2cents: