Join Date: Sep 2005
Location: San Tan Valley Arizona
For the past couple of years here in PHX, I have used 20w50 in the summer. It helps with higher idling oil pressure. Given that temperatures near the pavement can approach 140 degrees F on a typical summer day here, it's certainly not too thick for those conditions.
Now in the wintertime, it IS too thick, even for S. Arizona, and then I switch back to 10w30.
As long as you switch it out before cold weather sets in up in NJ, you will be fine.
I don't own an XJ any longer, but I still think they are the best of all the Jeep products ever made. My XJ was my favorite vehicle in my 50+ years of driving.
So...I stick around and give advice.