Jeeps have notoriously bad gauges. If it is an electrical gauge, I wouldn't trust it one bit.
I suspected my Jeep had a bad gauge, and was worried because it didn't move much and was reading extremely low after warmed up on a good hot day. So, I had my mechanic install a mechanical oil pressure gauge. Turns out, sure enough--my gauge was wrong.
Unfortunately, it was reading far too high. After being warmed up on a nice hot day, I had ZERO oil pressure at idle! Yikes!