I have a 1999 V10 F350. It doesn't "guzzle" fuel. With puttering around the farm, pulling a trailer once a week or so, it averages 10-11 mpg. On the intersate, running empty, I get 13-14 mpg. That's pretty good for a gas engine in a 1 ton, no matter how many cylinders it has :)
I too pondered...