I have a 1980 F250 and the gas mileage is about 9 miles to the gallon.Is this right for the 351M motor to suck this much? Thanks. Gary

 

If it has 4.10 gears and a c6 automatic, that's about right.

 

What about a 302 with 2.73 gears? I'm getting 8 miles to the gallon. Why does MY truck suck!?

 

fishin, you probably keep your foot into it until highway speeds with those tall gears, and for the reason of this thread, you gotta look at it this way... a brick has about the same aerodinamics as the early 80's f-series.

 

I would rebuild the carb. The old motorcraft 2bbls are famous for the power valve leaking fuel into the engine.

 

Thanks I think your right.I got a lot better mileage when carb was first rebuild 8 years ago. Thanks

 

Gary, I get maybe 8 mpg if I'm going downhill in neutral with the clutch in, and if I open up the 4 barrel, forget mpg it is more like gpm (gallons per mile) I can almost see the gas guage go down!!

 

a brick has about the same aerodinamics as the early 80's f-series.

Very well said my friend!!

 

There are many things that affect fuel mileage. Size and weight of the tires, size and weight of the rims, brake adjustments, condition of bearings, what kind of oils, greases you use, type of air filter, how well it is firing, the gear ratios in the transmission, the gear ratio in the rear end, how much weight you are carrying, condition of entire fuel system. What the weather is like when you drive, hot vs. cold, if you do highway or city driving, if you're heavy on the gas or easy. I'm most likely missing something. The less rolling resistance the less the engine needs to work thus better economy.

I find you keep everything well greased, use proper fluids, and keep the tires inflated properly, always have a clean air filter. It seems to help out alot, just something dragging a little bit sucks alot of fuel. I also find I get way better mileage with a 4 barrel vs. a 2 barrel as the primaries are smaller on a 4 barrel vs. a 2 barrel. So you could go smaller 2 barrel or put on a 4 barrel and have the extra oomph when you need it. I find that a rear end around 3.00:1 ratio yields pretty good highway and city driving and gives me pretty good fuel mileage.

I've never owned a vehicle that got less then 13mpg and that includes a 4x4 econoline van with a 460 and C6. The last two Ford trucks I had got 18 and 22 mpg, the 68 with a FE and 3.73 rear gears often got around 17-18 mpg, the 86 with a computer controlled 302 and 3.55 rear gears got around 22mpg. My 66 Merc with a 410 and 3.00 gears I've gotten up to 22mpg with and usually get around 20-21, unless I hammer it alot then I get less But a brick can only go so fast through the air and alot of drag can affect fuel economy, to overcome this you need a huge engine But I do almost no city driving and stop and go driving sucks alot of fuel.

 

Would this be the reason why i think i always smell gas in my oil?

I had the carb rebuilt about 1 1/2 years ago now. Worst decision of my vehicle history. I'm now finding that the guy who did it is an idiot. Not to mention he kept my truck for 3 months to rebuild the carb. Oh and he charged me $350. Yeah i was pissed. That was before i really started to do any work on my truck.

 

I do do alot of in town driving. But i'm rarely really getting on it and i try to coast as much as possible. I do all i can to try and spare gas because my truck does so horrible on it.

 

[quote=fepowerguy8;9253384]There are many things that affect fuel mileage. Size and weight of the tires, size and weight of the rims, brake adjustments, condition of bearings, what kind of oils, greases you use, type of air filter, how well it is firing, the gear ratios in the transmission, the gear ratio in the rear end, how much weight you are carrying, condition of entire fuel system. What the weather is like when you drive, hot vs. cold, if you do highway or city driving, if you're heavy on the gas or easy. I'm most likely missing something. The less rolling resistance the less the engine needs to work thus better economy.

I find you keep everything well greased, use proper fluids, and keep the tires inflated properly, always have a clean air filter. It seems to help out alot, just something dragging a little bit sucks alot of fuel. I also find I get way better mileage with a 4 barrel vs. a 2 barrel as the primaries are smaller on a 4 barrel vs. a 2 barrel. So you could go smaller 2 barrel or put on a 4 barrel and have the extra oomph when you need it. I find that a rear end around 3.00:1 ratio yields pretty good highway and city driving and gives me pretty good fuel mileage.

I have pretty much stock size tires on it, 235/75/15. I just replaced both front and back brakes completely so the dragging is a minimum. Just regreased all front bearings. Getting ready to put 3.50 gears in the rear end so hopefully it will help with in town driving.

 

If you smell gas in your oil, you most likely need a new fuel pump. Even if it is new. The quality of the new parts are horrible now a days. That will also help your mileage. The pump is always working if the engine is running. For every squirt of fuel to run the truck, a squirt is going in your oil. If your motor has wear on it, your oil level can stay the same. You may be burning the gas right out your exhaust.

 

Higher gears do not always make for the best mileage. My truck gets about 9 to 10, in town or on the highway (sometimes I can get to 12). I also have 3.55s and 33 in tires. I have wondered if 3.73s or 3.90s might make for better mileage, but in the long run, those start to out weigh fuel savings with cash outlay for parts.