Jeeps Oil Pressure

I have a 1994 Jeep Wrangler with a new 4 cylinder that I have put approximatly 20k on since ive had it.
With the old engine, the oil pressure stayed and was maintained between 45-60 psi and with this new engine, at first it was also the same. After time it began to get lower around 30 psi at idle using 10w-30 (recomended) and would not go above 40psi while driving on the highway. I thought maybe it was due to the cold weather and changed to 5w-30 which is also recomended as an alternative for cold weather. After doing so the oil pressure went back to what I saw as normal operating pressure for my jeep which was around 45-60 psi, Recently however, after about 800 miles with the 5w-30 the oil pressure peaked the guage at 80 psi is this cause for concern and what might this mean, other than viscosities of the oils? :