I have a 1982 Ford F150 , 400-2barrel, 4-speed, 4X4, I checked the gears in the rear axle by turning the wheel and counting driveshaft revolutions, looks like either 2.90 or 3.00 gears in the truck. (slightly less than 3 full turns of driveshaft to 1 turn of rear wheel- gears are for stock 6-cyl. truck with automatic trans, engine/trans is a transplant) So I am assuming the same ratio in the front. I've run 4 tanks of fuel through the truck so far, it's a 19 gallon tank. I write down the mileage at every fill up, and also the gallon reading off the pump, and figure my mileage.

The first tank of gas yielded 11 mpg, that is with front hubs unlocked, and 2WD only.

Next tank of gas got 9 mpg, with some 4WD useage and warmups, cuz it started getting colder outside.

It snowed and I started using the 4WD more often, and keeping the hubs locked so I didn't have to get out and lock them every time. Mileage dropped to around 8 mpg average. This is also with longer warmups to melt ice/snow off windows and get heat in truck, for taking my son to school in the morning.

Great truck, but the mileage is nasty !

Any advice ??

 

The 400 is a notorious drinker. Even in its prime in a 4X4 the best one could ever hope for is about 15 MPG, and add a little age and get it a little out of tune and 11-12 was extremely common (even less under load). Now that it has been over 20 years since they where installed in a truck your mileage doesn't surprise me. Other then the basics of a major tune up, I don't see your mileage improving much (good chance it is running rich). If it runs OK I wouldn't overhaul the engine to get 3 or 4 MPG out of it.

On the other hand I am sure you have realized the 400 has plenty of power and torque for any job you might attempt, and the a huge amount of miles can be racked up on one as long as its not abused. Shouldn't hurt your feelings to hear that the latest and greatest 5.4 in 4X4 form only gets about 13 to 16 MPG in real world driving and one can only guess what it will go down to after 20 years of use.

 

Yes the mileage does not surprise me, and most V-8 SUV and trucks today seldom get over 15 mpg in city/real world driving conditions, good point. Considering I got this truck for $1800, it was rebodied completely, and painted base/clear, I'm not complaining. I even managed to sell some spare parts I got with it for $400, so my actual investment is only $1400. It looks great and runs strong.

I was hoping for 13 mpg due to the low numerical axle ratio, but my gut feeling is the weight of the vehicle alone is causing the 11 mpg while in 2WD.

It's not rich, I rebuilt the carb and put in a new float, and the adjusted the idle mixture needle correctly for best idle quality. I could lean it out with smaller jets, but no doubt than driveability and power would also be sacrificed, there's no free ride.

This engine was rebuilt, but it is an older rebuild. It has yet to leave one wisp of oil smoke out the exhaust pipe, which I am highly satisfied about- being my old '76 with 360 FE smoked like a house on fire sometimes. Also, this isn't the best time to check mileage, as it's cold out and the choke is on for a longer time.

Thanks for the reassurement !

 

the best i have ever gotten out of my 351m is 12 mpg. it also has 327k on it now. has had bad main bearings since i got it at 42k 4 years ago. still have yet to do a tune up, why i have a new 460 waiting for this old m to die, i think is going to be a long wait. tick tick tick, sounds like shes ready to go, yeah right .. Kurt oh i have changed the oil in the trans and motor. i dont really want it to die, but why waste the money, it still gets 11mpg. i have installed the holley analog and digital tbi on the 400, and customers have seen an increase to 15-16 mpg and greater drivability. go with the closed loop set up.