The V8 enables me to tow and maintain highway speed (and thus, fuel economy)
Generally, higher speeds use more fuel.
As do lower speeds, especially combined with any associated stop and go traffic while towing. The jeep gets the best mileage between 60 and 65 mph sustained, 50 and 60 with a load. I've said it before--I can do it with a smaller, more economical engine. Problem is, I wouldn't be able to pass as well on two lane roads and thus, my mileage would suffer. If I put up some blue lights, blared a siren, and everyone got out of the way, that would work just fine. Problem is, it's illegal.
Most cars these days are designed to be aerodynamically efficient. But a Range Rover or a Jeep is more like a brick than a raindrop.
My daily driver has a 0.35 drag coefficient. This is actually on the high side, but it's designed to stay on the ground like the F1's you mentioned. It's frontal area is also less than 2 meters, which more than makes up for the high drag. I'd love a Honda CR-Z, but I don't have 15 grand.