I have a 1986 ford F-150 4x4 with the 5.8 H.O. engine in it. As far as i can see it is completly stock right now. The thing is is it only gets 13 miles per gallon. I thought there must be something wrong with the truck but when i went to fueleconomy.gov and looked it up it said right there in black and white that the fuel economy was only 13-15 mpg. My question is why such crappy gas mileage?? Does anybody know of any way of getting it to perform at a decent mpg. Would better breathing make any difference at all. Better KN air filters? Headers? Would they make much difference. And what is the thing with the 5.8 liter H.O.?? Why is it HO? And is it worth keeping? Thanks in advance guys

 

I get an average of 11 mpg (city+highway) with my re-built 84 and custom intake, and I'm glad to get that!
The "H.O." supposedly stands for "High Output", these came with the Holley 4-bbl. carb, different heads, cam, etc. for about 70 HP more than the regular 351W!!! [210HP vs. 139HP] The best way to maximize fuel economy is to keep your foot out of the gas pedal, cause the carb's secondaries will open up and guzzle the gas.

 

13 mpg is quite good in my opinion. I have an 86 f150 2wd with the 5.8 HO and I average 12 mpg driving mostly on 2 lane highways.

 

My '85 HO, 2wd, only gets 10 mpg and it's geared somewhat higher (3.00 rear, c6 tranny).

find out what size your rear end is (on your pickup, that is).

That'd be something you could change, but if you pull anything such as trailors, you may want to keep a lower gear ratio.

If you have a c6 tranny, your mpg will be worse than if you had a AOD.

Just some ideas.

I'm also gonna be junking the 4180 Holley carb on it and getting an Edelbrock 1406 real soon. I hope to see some small improvement with this for my gas mileage.

 

My 86 4x4 has the EFI 302, 3:55 rear, and 4 speed OD, and I get about 11-12 MPG around town. That's not hot rodding or anything either. If I drive like granny, never go over 50-55 and shift 2-3 really low, I can squeeze 13-14 out of it. Dad told me he got 20 in it on the highway before, but I think it's the older you get-faster you went kind of thing. I don't think it would ever get that.

According to that web site, I should get 14-16, yea right!

 

You're doing pretty well at 13MPG. My 86 351 H.O. extended cab 2WD 3.50 gears gets about 10MPG. We just towed our 5014 LB camper to Florida on vacation last week and we averaged 7.5 MPG.