So, second fill up down - closer to EPA City at ~16.3mpg.
19.4 gallons on 316 miles. Possible handicaps: found a crack in the radiator side tank, so running with wired-open cap vent for 0PSI system and still getting some dribbling. Also, truck started reverberating horribly on Thursday on my way home from work, seems vehicle speed dependent (same major noise in 3rd, 4th, 5th gears) and is only bad when engine is loaded (lots quieter when clutch in). Minor improvement in noise made when I pumped ~50PSI into the rear air helper shocks to reverse some "butt sag". The rear leaf spring shackles are rubbing on the trailer hitch receiver mount - it is bent a bit. I think it is transferring noise from the driveline, and could be exacerbated by a "rear end sag" condition.
Most likely: truck gets worse MPG when only going the ~11 miles one way to work from cold start, then cold soaking for 9 hours, and doing it again. (Cold here being less than 10F for the past few weeks, with several nights at -1 to -10F.) It isn't exactly city driving, but it isn't steady-state freeway driving either, and there are no "more constant speed" alternate routes, although I could potentially skip a 45mph section for a 50mph section and an extra mile, and making one "turn at a light" into a "stop at a light".
Maybe when I put in the new radiator/hoses I will put in a block heater. I'll have better access with the radiator out, and I'll be making a mess/draining the system anyway, so why not? I can always finish this tank of gas before plugging it in - though I doubt I'll want to wait. Takes ~1 mile to get off C, and another mile or two to normal/good heat output. (heater core may have a bubble in it, too, thanks to the leak...) I also notice a sharp temp drop at mile ~7 when the thermostat opens.
Any downsides to installing a thicker radiator core, if it will fit?
Automatic-equipped Explorers got double-row radiators - my manual truck has a single-row. Not sure the fan shroud will fit the thicker radiator, and the salvage yards are all frozen tundra right now though I'd love to pick up a metal fan off an older Explorer to replace my cracking plastic one.
Gotta save my pennies and figure out a Scangage or similar. The MPGuino sounds like a more accurate MPG gage, and there are other scanners than Scangage that have better access to the Ford subsystems (read/reset ABS codes, etc.) but they tend to use a tablet or phone.