Quote:
Originally Posted by Frank Lee
If you want fuel economy you're going to have to slow it down to 55 and/or seriously aeromod it.
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When you say fuel economy, that's a relative term. I'd be happy to get above 15 mpg right now, because my best tank so far was about 14, and that was all highway miles at 60mph to keep the rpm below 2000. One of my recent tanks was about 9 mpg, which is totally unacceptable. On long trips I hope to get in the neighborhood of 18-20 mpg, which I think is still possible at 65 mph considering that my father's old '77 F-250 4x4 with the 4-speed, crew cab and short bed did 21 mpg at 65 mph.
That's with heavier running gear, heavier curb weight, loaded with about 2000 lbs. of payload, no overdrive, higher ride height and a bigger displacement carbureted engine (351M) along with old-school heavy weight non-synthetic gear oil and taller/wider mud/snow tires. This was no spread-bore 4 barrel Motorcraft carb either, it was a 2-barrel that was quite a bit worse for efficiency. That truck was not the model for high mpg, but if we saw those kinds of numbers with that setup, I can get those or better with this one. I think my expectations are relatively modest considering that it's fuel injected, smaller displacement, much lighter, lighter running gear, is 2-wheel drive and has a lower ride height.
As far as aero mods go, I do plan on at least installing a bigger air dam, and maybe more depending on what that yields. I intend on adding a vacuum gauge to mod the nut behind the wheel as well. In addition, I bought a scanner tool to be sure that all of my engine sensors are reading within their specified ranges.
That said, my first concern is utility. This is a work truck that I don't drive every day, so that's the priority. If anything else interferes with that, it's gotta go. I chose the 300 because I've seen them run for 30K miles with a loud knock in the engine and no oil changes. I've also seen them run 300k miles with no bottom end or head work needed, the rest of the truck rusted in half around it, on its 4th c4 transmission. I want that kind of reliability, and unless you go with the light duty Japanese trucks from that era, you can't beat the setup that I'm building.
I owned a couple of old Nissans as well, and their mileage wasn't much better considering the gearing they needed with those smaller engines to keep the truck moving on the highway. I also like that this engine has peak torque, 265 lb-ft. at 2000 rpm, which is what you need when you're pulling a lot of weight. I don't want to have to rev a 302 to 2800 rpms just to get a trailer moving, and I don't want to go bigger displacement due to economy concerns.