When I first got my van and it had 3.73 gears and stock bumpers and no roof rack, I would get over 15 cruising on the highway.
Now that I have 4.56 gears, deer-proof bumpers, duals, and a full safari rack I get more like 12-13 hwy and 10 in town.
Towing I get 7-10 (depending on load and speed), but when I had the 3.73 gears it would be more like 6-8.
But.... Gas is cheap, and the V10 is a very durable motor that needs few repairs, and maintenance is cheap if you are willing to spend a few hours in the driveway every 100,000 miles.