Just took my new ride out on a 240 mile trip. Averaged about 13mpg at 60mph. What is the factory specs for MPG on a 1982 4.9l auto 2wd? My other '82 with a 3 speed manual gets 15 mpg. Does the automatic have that much difference in mileage?

 

You will lose 1 to 2 mpg gallon with the automatic(torque converter slip) and your rearend ratio may be different. Look for a tag on each rearend or look at the rearend codes on the door jamb of each truck. Write back in with the codes and we can look them up and tell you the ratio. If the 13mpg truck has a higher number in the rearend, that's where the other mpg is going.

 

Thanks Dave, checked the axle codes; the auto has a 17 (2.75) and the manual has a 13 (2.47). Might swap the 2 out some day as the auto is my daily driver starting tomorrow and old red is being retired for wood hauling and bad winter days.

 

My '89 EFI 4.9L gets around 17mpg on the highway (doing 55mph) though.

3 speed C6, with 2.73 gears...

I know it's EFI vs. carbed, but i've always seen these older carbureted engines get better mpg than the fuel injected ones!

 

I think you have those backwards. Axle code 13 is 2.75, axle code 17 is 2.47.

 

Sometimes.









Source: FoMoCo 1980/1989 Light Truck Parts Catalog (available on CD from hipoparts.com)

 

I know they liked throwing the codes around with the change over to the 8.8" but since he said he had two 1982's I already knew the codes from memory and didn't list one of the many exceptions to thse trucks .

If he said he had an 83-86 I wouldn't be sure about the codes, because I have seen 9" rear ends factory installed in 1986 F150/Broncos.

 

No biggie, it gave me an excuse to go post all those pages.

I look at it from the point of who is going to be looking in these threads in the future (perhaps via Google) while researching their own truck.

While your post may be true, it's only in the context of, in this case, 1982, whereas the forum covers 80-86.

Just wanting to keep things as accurate as can reasonably be....

 

You didn't say if you've tuned the new truck but, if not, that can easily account for several miles-per-gallon. I haven't as yet gotten a good read on the mileage on Dad's truck, but I know it'll be much better since I took the initial lead from 10 degrees ATDC to ~16 degrees BTDC, and I fixed the blown vacuum advance.

I'm not saying yours has either of those problems, but it could and either of them will kill your mileage. Yes, plugs, wires, caps, and rotors can hurt the mileage, but usually not kill it the way timing will because timing works on all cylinders and only the rotor of the other stuff does.

 

My truck is a '86 with the 4.9 and a T-18 4 speed trans. The rear axle has 3.55 gears (code 19)

During the summer when I drove it everyday running a lawn service business, which included highway, city, and everything in between I got a steady 13 mpg. On long highway trips I can get close to 15 mpg but I have to keep it between 55 and 60 mph (So getting passed by big rigs on the interstate is normal )

I'm not sure what the factory mpg ratings were for these but I know that the numbers they got in the 80's were VERY optimistic. I've heard that they did the test on dyno's which did not simulate real driving and the strain that is put on the engine.

 

The EPA did their tests on dynos with an average speed of 48 MPH.

It is quite possible to get the estimated EPA in your vehicle though with the right gearing and tires combination, and driving at 55 MPH. This is with a stock engine with stock cylinder bores.

The EPA rating for a 1982 4.9L with auto tranny was an average of 18 MPG back in 1982.

 

Hmmmm, I got 10.7 MPG this last fill-up with the 1984 300 I6 with a 3-speed manual gearbox and a 2.47 axle. That was with a pint of seafoam in the tank, though, so hopefully that's what made it so bad.

I was figuring it probably got about 10 mpg when I bought it, but after finding out it had that low-ratio axle, I was hoping it would get better mpgs.......... :<

 

I get 10 mpg and those are imperial gallons with my 4.9 carbed 4speed 4x4 and I drive like it like I am running on empty enroute to gas station..My 79 4.9 2 wd got 15 mpg in town with a 3 speed manual

 

How are people getting these supposed 22-28 mpgs with these things? O_o

Living in the flatlands? I have to pull a /lot/ of 9% grades with excessive twisties around here, in 2nd gear....

 

Mine averages 21 MPG at 55 MPH. 300-6, T-18 4-speed, 2.75 gears with 225/75R15 tires. Completely stock except for one size larger tires.

If you haven't done so yet, I would read this thread here. It's got some great information that might help boost your mileage.

https://www.ford-trucks.com/forums/1...hing-else.html