This is a more or less a rant, but one of profound merit (to me at least)! I just took my 78 F-350 dually (460/C-6) from Sandusky, Ohio to Holland, Michigan and back. It's about a 220 mile trip one way.
I filled up both tanks (19 gallons in each tank) and headed out. Well, I used up my front tank about 105 miles into the trip (close to the 1/2 way point) and switched to the rear tank. By the time I rolled into the Holland city limits, my fuel gauge was screaming EMPTY! So I topped off both tanks again and drove the 3 miles from the gas station to my destination. The following day I drove around Holland for about 6 miles total, loaded up a riding lawn mower in the back, and headed home the following morning.
The return trip yielded about the same results and I was out $150 in fuel costs for a weekend trip. My math isn't the greatest, but even if I called the distance I drove an even 450 miles, using 76 gallons of gas, that equates to a horrific 5.9 MILES PER GALLON!?!?!?!
And I've got a fiberglass cap on the bed to help cut down the wind drag! Needless to say, I'm more than slightly upset about it. I run a 600 CFM carb on the ol' 460 and now I think I'll switch to a one barrel off of a 300 I6! I'd love to hear from the other 460 owners out there who have had similar issues!! Or even better, the ones who get 10 to 18 MPG out of em!! Lets here ya!!!

 

hmmmmmmmmmm, how fast were you driving? have you checked for leaks? gas cap seal good? lots of little things could cause this, but i have a feeling it will be one single thing.

 

My 90 f350 dually 4dr,460,4.10,at averages about 11 on interstate empty.Towing 16ft landscape trailer loaded,about 7.

 

dont know what to say really, i only get 8-9 on my 73, whether i get into the throttle or cruise easy, so i feel your pain on the gas thing.

 

I averaged about 65 to 70MPH most of the way. No leaks at the tanks or fuel lines, I repaired all of those already. Is the ONE SINGLE THING my right foot? I hope not!!

 

https://www.ford-trucks.com/forums/s...ht=fuel+economy

Here is my take on Fuel mileage.


By the time you are finished reading this you will be able to answer this question


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Considering the FACT there are so many variables regarding fuel economy it would be hard to get a specific answer.

Things to consider:
1)Quality of Fuel
2)Additives
3)Tune & Efficiency of Engine
4)Altitude
5)Driving technique (speed,Start-outs,etc)
6)Topography where you are driving
7)How much city/how much highway driving
8)Gear ratio & size of tires
9)Weight of the vehicle
10)Tire inflation
11)Vehicle design (drag)
12)Clean air filter

Just to name a few.

I drive a 78 pickup with a well tuned 429 engine,at an altitude of 3400 ft above sea level,with normal weight on the truck with a canopy,tires inflated to spec,using premium fuel,2.75 rear,C6 Trans, With my foot on the pedal like there was a egg under it, in Canada in a city that the downtown is located in a valley.

I get 14 city & 18-19 hwy.

Does this help ?

 

I get horrible gas mileage in my 94 F-150, 302 V8 with AT (not sure of how many speeds.. 3 maybe?). I think I got 6.4 MPG on the expressway doing 70 mph and 3 just dicking around the city. I think it has something to do with the O2 sensors though.

 

I'm going to read Dennis' thread a little later on, but my 460/C-6 got 10-11 mpg on a trip around the southeas states.
When my milage dropped inexplicably I finally discovered the Auto Choke piston was sticking and allowing the Choke buttefly to close slightly.
I dont know what to do about that piston either. It just wont stop sticking.
but when I locked the choke valve open, the milage went right back up.
And that 460 dont care about your tailgate down, or your Tonneau up, or what you do with your right foot. It's gonna burn a given amount of fuel based on the amount of air you can feed it.

 

[QUOTE=Mil1ion]https://www.ford-trucks.com/forums/s...ht=fuel+economy

Here is my take on Fuel mileage.


By the time you are finished reading this you will be able to answer this question

Dennis, I tried that link and it took me to the home page.
So what do I do next? and dont tell me to learn to read.....

 

My 78 f150 4X4 short bed with a 351m/400, edelbrock intake and holley 600 gets around 8-10 on the highway. That's up from the 5 to 8 since I changed from 33 inch off-road tires to 31 inch street tires. When I pull my 23 foot camper (4000lbs empty) I haven't measured (I'm too scared) but it's a lot less. If anybody has any magic answers I would be glad to hear them.

 

make sure the tires are properly inflated. if its a dually, I assume 235/85LT16s which max out at 80 psi. I keep mine close to that.

second, Crane Cams makes a roller fulcrum kit that replaces the stock rocker fulcrums with needle bearings. in my 73 F-350 it was good for one mpg. replace the 73-later timing chain set with a 68-71 set from a lincoln. this will greatly pick up power, and also increase MPG. be sure your timing is properly set. I like 6 degrees, but your altitude will affect that. do you still have all the 1978 emissions installed? if you dont need them to comply with smog laws, box them up in the garage. they rob power, and reduce efficiency. and edelbrock intake and 650 cfm carb of your choice properly set up will help a lot too.

what are your rear gears? my 79 duallt flatbed had 4.11s and sucked gas like no tomorrow. consider 3.73s, or 3.55s or an aftermarket overdrive unit. teh 460 has more than enough torque to use a steep gear set.


if you have 8x16.5 tires, and 4.10s there isnt much hope...

 

So you increased your MPG by going from 33 Offroad tires to 31 streets? Jesus, I'm going from 31 Streets to 35 offroad tires :|.

 

the crane rocker fulcrums and a 1971 t/c set will work for the 400 also.


also use thinner oil if the engine is new 10/30 or so older engines can use 15/40 diesel oil.

 

Teepee,
The reason your mileage went up is because your tire circumference went down. This means you didn't gain squat. The truck says it went the same distance but, it actually went a shorter distance. Taller tires get you better fuel mileage.
If your hurting on mileage the best way to fix it is, to change your rear end gears.
Look at Dennis, he's got 2.75's. He's getting 18-19 on the highway with a big block. That's incredible. I imagine he's cruising around 65 or 70 MPH.
If you have 4.10's then you'll be lucky to go 65 or 70 MPH, and if you do, you'll get 8 MPG.
Secondly, the only way you could increase mileage buy changing rocker arms, is to change the rocker arm ratio, thereby changing your valve lift profile. I seriously doubt, rocker arm friction is costing anyone any gas money.
Consider it,
KingFisher

 

I second the tire size difference. I run 33's with a difference of about 10% less on both the speedometer and odometer. The speedometer/odometer was calibrated for a 29" tire. If the odometer says I have traveled 100 miles, I have really traveled 110 miles, which helps when figuring gas mileage.