The diesel fumes from an 09 or 08 engine would be better for the horses then the gas engine. Diesels also always run with excess air, so no CO emissions.
I have a 2008 F-250 6.4L Powerstroke 4WD with 3.55:1 axels. At 65 MPH, 70 mile trip, 2 dirtbikes in back, it averages 18 MPG. Or 12 MPG on 10 mile trips when there isn’t enough time to average the warming of 15 quarts of oil and 7 gallons of coolant. Once warm I can keep the MPG display above 20 depending on how much I have to stop.
When the truck had less than 400 miles we hitched a 6,000 pound toy hauler and drove 370 miles at 70+ MPH and got 8 MPG. That should be worst case because the rings did not have a chance to break in. While it consumed more fuel, it pulled that load effortlessly.
As for the engine, it is designed and built by International who has at least as much experience as Isuzu, Detroit, and Cummins.
Except where noted above, all MPG numbers are calculated at the pump, not based on the fool computer.
The turbocharger is now an integral part of the emissions control system. I don’t think you will find a diesel meeting current emission standards without a turbocharger.
Old diesels rarely used direct injection, the current Powerstroke does and may squirt 5 or 7 times per combustion cycle which reduces the diesel rattle and controls emissions. EGR is heavily used along with the turbocharger to control the combustion.
The direct injection is also used to dump raw fuel out the exhaust when burning the soot out of the Diesel Particulate Filter.
Whatever you do don’t buy a ford diesel. If you do, get ready to spend a pile of money. I have an 03 f-350 with a 6.0, & after $4800 it still has issues. If I ever get out of mine I’m getting a Dodge with a cummims diesel. Been there, done that, & I’m sorry to say, still doing it