Fuel mileage largely depends on how you drive,
frontal surface area of your trailer, terrain, and gearing of your rear
axle.
I've found that towing at about 62-65 mph nets the
best mileage regardless of which truck I use. I see folks going way
faster, and could certainly do so if I wanted, but I don't feel safe pulling the
trailer above the posted speed limit and generally am happy to cede a few miles
an hour in the name of safety and distance between me and whoever's in front of
me.
Tire inflation on truck and trailer is critical,
too.
As far as Cindy's brake question goes, it may
be possible that bigger brakes are available for the F-250, but those probably
will cost a few dollars. Probably the best you can do, at a relatively
inexpensive price, is to make sure your brakes are within recommended wear
limits and that the entire system is otherwise up to date on its
servicing.
There are some power mods available for the V-10
engine (chips/programmers, etc.) but I wouldn't go there, quite honestly.
As you can see I tend to be a minimalist when it comes to throwing money to
improve vehicles and prefer simple maintenance... modifications and
"improvements" get expensive quickly and can prove detrimental to
safety/longevity of your truck. You see folks with all kinds of gizmos on
their trucks, passing everyone in town with huge trailers in tow, only to
require very expensive repairs later... not worth it. My cousin has done
endurance all over the southeast for YEARS with nothing more than an old Dodge
flathead six or an old Ford inline-six cylinder engine. I think her 1994
Ford had over 250,000 on it a couple years ago, original engine. She makes
it to every ride and up every hill, with two horses in tow.
>>>BTW - my 06 Chevy Duramax gets 13.5 MPG hauling.
My 1994 GMC with 175,000 miles gets a little over 12 mpg hauling...but
I'm starting to be more concerned with how many miles it gets to the
quart of oil! :-P The air conditioning quit working so I paid $90 for Fri-on
(sp?) & some stop leak, since it was leaking it apparently. I had GREAT
air conditioning for maybe...12 hrs. Guess the leak is bigger than they
thought. So...no air, burning oil, radiator's leaking, radio only works on
maybe one channel....but it's paid for! :-)