[LetsJet]

I think I read in the HO engine it required 10w30, but I can't find it.

Here is what it says from WJjeeps.com

"Oil Capacity: 6 Quarts, 10W30 recommended"

This is a good site for oil info

http://63.240.161.99/motoroil/oildatasheets.html

As you can see, if you are talking Mobil 1, there isn't much difference in the two except at startup. I think the 5W is a bit better for most vehicles as it will start lubricating quicker.