Just curious what's everybody getting in a f250 4x4 with the 351 and the 4speed manual

 

1977 F150 with 351, 4-speed and 3.50 rears returns 17 HWY.

 

Depends on your gear ratio, tire size, and type of driving, but I've seen people get as low as 8(for normal driving), and as high as what FoMoColover said=17mpgs

With stock gears, tires, and no lead foot w/ a tuned up engine, 12mpgs would be fairly easy.

 

76 F250 4x4 w/ 390 4spd & 4.10 gears = 12 mpg highway & 8 around town. You should get a couple mpg better than that since the 351 is less thirsty than a 390...maybe 14 mpg highway.

 

That's pretty impressive.

I had a '79 Bronco with the 351M/C6. The best it did was 15MPG highway. I used to drive it to work when gas were $1.20/gal.

 

Jermafenser, Mine was just like that.

79 351M/C6 3.50 gears 31" tires on the hwy taking it really easy, I once got 15.5 MPG after a nice tune up.

 

Ohh, yeah. Mine had 33" tires and 3.50 gears going at 60mph or so.

 

The Automatic will eat up more gas than the manual tranny will, I think 15 MPG is awesome for that combo, and vintage. Most people around here get 8 to 13 MPG with late 70's Fords. Supposedly the bigger tires will help your mileage on the highway and longer trips , but they hinder your off the line which also hinders fuel economy in stop and go and short trips, but I don't think there is any truth to that. Someone needs to call Mythbusters. With 70's Fords doing that good you would think the new ones could get 20 MPG easy you know. BTW do the 351 and 400 get the same fuel economy if driven the same.

 

Yes, I'm aware of the automatic transmission power robbing.

It pays when you pay attention to what's under the hood. Always tune it, and with good equipment. Replace what needs replacing, etc...I'm obsessed with maintenance. And good parts. Funny thing, when i sold the Bronco to the new owner, he found metal pieces in the oil pan but still ran well until a valve let go.

I don't know what to say about the bigger tires. With only two inches of extra meat, it couldn't make that big of a difference. It launches much easier, goes down the highway with less rolling resistance, that's for sure...but steering was never easy, haha. Couldn't comment on 31"s, the Bronco always had 33"s.

 

Bigger tires = Lower RPMs. I noticed my tank doesn't seem to empty out as fast on the freeway lately.
I'm running a 400 C6 4.10s and 35s and get about 8-9 street and 11-12 highway. The engine & tranny were rebuilt under 2000 miles ago, so that's also a deciding factor. IMO, if you're running one of thses big ol' bricks, you shouldn't bother stressing on MPG. No matter what you do, you won't get them up that high. Just enjoy the ride, and the fact that you're driving something you enjoy.

 

Actually, that is the exact trueth. It lowers your affective gear ration, giveing you lower RPMs on the hwy, giveing you better gas mileage, but it also affects take off and acceleration(more sluggish).

 

I've owned my truck for 25 years now, so I have it's tendencies down. It originally came with a 360 V8, which was later changed for a 390...no difference in mpg, maybe the 390 was slightly better. The 351 you have is a decent motor on gas, better than a 390 is.

The truck actually came with 7.50 x 16 mud and snow tires on split rims (which are no longer legal, due to some terrible incidents during changed tires at some tire shops). I have 2 sets of tires for it 35" BFG's and LT275/85R16E radials on solid rims off of a late 80's F350 4 x 4. The 35's do get a litter better mileage than the smaller tires do.

Overall the mileage is fairly consistent, what hurts me is that my truck sits to much. The more I use it, the better it runs and the better mileage it gets.

I think that if you can get between 12 to 15 mpg highway, you are not doing bad. It's not a Honda Civic Hybrid!