Well we have recently purchased a low km 2004 Patrol with 3.0L turbo diesel and I presume the Navara would be fitted with the the same motor.
According to research we've done, it is very fuel efficient, especially when towing. We are awaiting delivery of our 21' caravan so haven't had a chance to try out towing yet but so far are very impressed with the fuel economy and the "grunt" compared to our 1990 4.2L petrol Patrol.
The Navara has leaf springs the Patrol independent suspension . Recently as last May drove a mates 3.0 lt Patrol across from Perth towing a 17 ft Jayco Expanda averaged about 13/100 no head r side winds . Would assume the Navara would do about the same.
Have had front and rear suspension sagging problems with only 80000 kms on the clock. Get it checked out by someone who is knowing these things and how to check the ground clearances
__________________
Pets are welcome but children must be leashed at all times