I have a 2001 V-10 5 spd that I bought new in 2001. It now has 45,000 on it, and the best milage I ever got with it was 14.7MPG it has decent power, not what my old big block chevy had, but myold truck only got 6mpg, so I guess it's an improvement. BTW my old truck was dyno'd at 435hp, so that explains the differnce. It is a good, truck, but I have mine up for sale, as I'm tired of making payments for soemthing I can't afford to drive because of the milage. It stays parked and I drive my car everywhere.
As to milage while towing, I usually get around 6-8 mpg when pulling my 24ft travel trailer.
George