I had a 73 1/2 ton with a 300, and a 84 chevy 1 ton with a 454, and they both got about the same mpg.
ok that's believable.......not.
notice you said "about" the same mpg.
something was wrong with the 300 if you were getting the same as a 454. you must have been driving around in 1st gear at 40 mph, pulling a trailer, and flooring it at stop signs to get 6-8. the 454 is a beast and will of course never get more than 11 mpg stock.
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Kevin
1979 F100 4x2,
300 Inline 6,
3 speed manual,
9 inch rearend,
10 series Flowmaster,
Grant steering wheel,
JVC stereo in the glove box-the previous owner did that,
and some other stuff
"You got to drive that Ford like it's a stallion."-Jack Ingram & the Beat Up Ford Band
I get 11 - 12 out of my 300. Sounds kinda low but I'm pushing 39.5 tires, and it's stuffed with a 260H cam, roller rockers and a Demon 4 barrel. I've owned both the 351M, and 400, and I'll take the 300 over both of these any day (especially the 351M). The 400 responds to mods pretty well (it's just a stroked 351M), but you are looking for fuel mileage so that's out. With the right gear ratio (2.70 - 3.08), there's no problem getting 16 - 18mpg out of the 300. If you do the swap, I would seriously consider an intake swap, and a Motorcraft 2 barrel, along with a set of late model exhaust manifolds from a FI 300 (so you can run true dual exhaust). It's a great combo, and with a 4spd, you'll forget all about that 400 you used to have.
