I’m no Jeep expert, but I had a buddy that was the sales manager of the largest car dealership in town and I asked him once what engines they saw that seemed to last the longest. He said that they see the most miles on the 4.0 Jeep, 4.6 Northstar, 3.0 Ford and 3.8 Buick. That was a while back, but given that, I’d opt for that 4.0 in your daughter’s Jeep if you can find one.