I bought a 2000 cherokee sport this past august. I changed the oil and filter myself. This morning when I was driving I looked down and the oil pressure gauge was maxed. First time its happened since I had it. Cd it be because it was extremely cold. 10 degrees F for the past few days. First time I drove it in 2 days, I got back and waited 10 mimutes and started it back up amd it was back dowm to the usual 40-45.

 

The cold temps make it higher initially, but bad oil pressure senders are very common, swap it out with a Mopar unit not a cheapie!

 

Sounds like your oil pressure sending unit might be starting to go bad...when they go bad they max out the gauge

 

I had the exact same problem last winter and it was the sender very simple to change and if you don't want to keep replacing it get a good one first (just speaking from experience I bought two cheap Oreilly ones first)

 

What weight oil did you use? You may be better off using 5W-30 oil if that is not what you are using.

 

I used 5w-30. Valvoline maxlife. A puralator gold oil filter when I changed the oil