I bought a 1989 F150 Shorty 4.9 M5OD with 3.08 gears, 235/75/15XLs. It was rated at 27mpg highway while the 89 Ranger 2.9 auto was only rated at 26. I bought the F150 with my 125mile round trip daily commute. I didn't think it would actually get it. For a couple weeks I drove it like I stole it to break it in, after that, I shifted at 2500rpm in every gear and I did get a consistent 26-27mpg!
In the winter that was a completely different story! I like in SW Ontario CANADA and our winters can vary a lot . Winter mpg anywhere from 15-19mpg.
A friend of mine work at a local auto parts store and suggested that I try a newly available 205 degree thermostat to bring up my operating temp.
Voila that made a huge difference. It increased my mileage 2-3 mpg in cold weather , but no change in the summer.
This truck pulled fine but mileage on a haul from Deming NM to 3hrs NE of Detroit got me a wopping 13mpg, and I could only use 5th on flat ground. It was hauling a 70 F100 shorty on a tow dolly.
If you want fuel economy with a 4.9 warm it up and keep your rpm down!

 

would porting and polishing the head, adding a better cam, putting on a header and putting in a higher than normal thermostate actual help (i always thought u kept them cool and they run better??)and be worth the money?? because i do all my own work and and have thinkin bout upgrading my truck a liltte...

 

Holy thread revival!!!

 

I've been trying every simple thing in the book to get my 87 4.9 4 speed 4x4 with 3.55 gears more MPG. I got 31's on it, new O2 sensor, regular tune ups and oil changes, clean the intake, new walker y-pipe, new thrush muffler, stock tail pipe, bug deflector, lund visor, shift at 2500 rpm every gear usually, run about 70-80 mph on the highway, keep up on my tire pressure, coolant level, oil level, just put in a new clutch in the summer, new brake booster, new calipers, new brake hoses, half the lines are new, new pads and shoes, adjust the parking brake so it doesnt rub. new computer 2 yrs ago, cleaned the MAP sensor, cleaned all the electrical connections, bunch of new sensors, etc etc

i've done pretty much everything I can think of without tearing the engine down and putting new expensive stuff in it. but I get about 12-14 highway, I guess thats pretty good for how fast I drive in these mountains of Appalachia, up and down, side to side, steep and gradual

 

You're not doing every simple thing - as one of the simplest things to do is to drive slower!!

Drop down to 50-60mph and you'll pick up 2-3 mpgs (or more) easily. Your wind resistance is related to your speed SQUARED, so even a small increase in speed causes a significant increase in drag.

 

I've tried slowing down, I just like driving fast, but thats my own fault, I wanted to do everything else besides that to help my fuel economy

 

be happy with the mpg you get, bud. i get 15.1mpg at 55mph. 9.4mpg <--best recorded in town. i don't even romp on my stuff either. i babied that truck like it just rolled off the lot yesterday. i've also tried flogging it to see if it would change and it sticks around the 9mpg area, flogging or babying. what i've done is a cat delete, thrush welded muffler, 31x10.50's (running 45psi rear and 35psi front), and a complete tune up and new ecm.

EDIT: I run around in the winter in 2wd with hubs unlocked. i only use 4x4 when absolutely needed.

 

what i've done is a cat delete, thrush welded muffler, 31x10.50's (running 45psi rear and 35psi front), and a complete tune up and new ecm.

EDIT: I run around in the winter in 2wd with hubs unlocked. i only use 4x4 when absolutely needed.[/QUOTE]

Ive done all those too, except for the different tire pressures, maybe I should try that, does it seem to help any? I run all the tires at 45psi. If its snowing or going to snow I keep the bubs locked in and leave it in 2wd until I need it just so I dont have to get out and lock in the hubs. But when the roads are fine I unlock the hubs, esp on the highway.

 

the difference of tire pressure doesn't really make any difference. i just go by what the door tag says. it told me 35psi front and 45psi rear, so that's what i run. if anything, the 45psi all around should reduce all around drag. no matter what i did/do it was always strictly 15mpg hwy and 9mpg town. you could try a taller gearset. longer legs might help with the hwy mileage. i've got 3.55's and personally like them and don't complain about the mileage anymore.

if possible, get some hard compound tires for summertime driving. my neighbor from my hometown had a '95 dodge 1500 4x4 318 auto that he regularly pulled mid 20's with it because he ran "pizza cutters" that were super hard compound work tires.

 

You guys gotta ease up on the pedal a bit.

I set the cruise at 60mph and just tag along for the ride. I easily get 17-18mpg out of the truck. She's no single cab/short bed 2wd either, she's a supercab/long bed 4x4 with the 5.0 and 3.55 gear's. I think the AOD helps too, it's geared decently high. On my 31x10.5x16 BFG's it'll sit at 60mph at close to 1500rpm.

 

I really appreciate the information I am seeing here. I have been contemplating a motor swap for a while and am currently looking for a donor truck. I have a 79 Ranchero for a daily driver that I really use as a truck and tow an 18’ trailer when I need to. For my daily commute I drive about 80 miles round trip and have 300 to 600 pounds of tools and equipment in the back most of the time. I think I want a EFI 300 6 with a 5 speed. If I were making a Christmas wish, I will put pistons in it to bump up compression, a torque cam, roller rockers, port and polish head, headers, and dual exhaust. Since this would be a retrofit and I have to rewire anyway, what computer recommendations do you guys have? I want good performance, but MPG is very important.
I am certainly glad this thread was resurrected, Thanks guys…

 

Ive got a 94 regular cab 4wd with the 300 and a 5 speed and I drive about 40 miles round trip a day to work. I drive 55 since that is the speed limit on the road I take. I have 235/75/15 mud and snow tires and only get 13mpg's. I don't drive it hard and I don't know what rpm I shift at or it is running at since it doesn't have a tach. This sucks since I have been getting over 20 out of a truck that I just sold but it wasn't a full size or a Ford.

 

that ain't right. sounds like your truck needs a tune-up or something. transmission make any noise? hubs locked or unlocked? tire pressure? diff oil last changed? tranny fluid last changed? are you hauling extra weight (loaded or unloaded)?

something doesn't add up. my 87 regular cab 4x4 gets 15mpg hwy at 55 and i have the c6 auto (3 speed auto, no overdrive) and believe me, she screams at 55mph. and i'm running 31x10.50's on mine.

 

---I hear that. I've got 213,000 miles on mine with nothing but straight pipe into a y-pipe w/ flomaster 40 2.5" , an EGR delete.
Getting 12mpg. It's the mountain driving-- i'm in Maui, Hawaii and its upand down all day. doesnt matter if i nascar the truck shifting @ 3200 or drive like a grandma trucker...

Only trick i've got is when i drop down to 10mpg...i pull my vacuum line off the intake or the cruisecontrol line and let the engine drink pure NAPTHA...until it chokes out. Blows white smoke...kinda like using seafoam but better...
that gets everything back in order to 12mpg

and i run 92 octane just to keep it clean...
still got the stock pistons and heads...

Tires are 31x11.5 grade D KTM KO klaws -- kinda like mudd tires. Made NO DIFFERENCE if i had on 235x70 's....strange.

harder tires though will boost your MPG...that;s the only thing i figure was different...these D's are a little more load barring

 

from what i've heard, the 300 efi's don't like long duration cam. aggressive profile, short duration, higher ratio rockers, 240 cylinder head, flat topped pistons, port and polish, efi exhaust manifolds (flow ALMOST as good as headers, the 3 into 1 manifolds), and a good set of smaller diameter pipes (2" ought to do it) going into some good ol' turbo style mufflers. also, drop in some 19lb injectors. that thing will rip then!