Gas mileage results for 4.9L in F150
 

From time to time, someone asks what mileage should be expected? Here are some records I have kept as I work on my personal truck. The truck is a 1986 F-150 short wheel base with 4.9L engine and 4 speed overdrive transmission. The rear end has a limited slip with 3.08 gears. The tires are Michelin X Radial [automobile] and are the original 215/75 X 15 size pressured to 35 PSI in front and 32 PSI in rear. It has 132,000 miles and still has the original catalytic converters (2) and muffler.

I purchased it in March of 2008 from the older gentleman who is the original owner. It was still almost original and needed TLC. It still had the original plug wires as well as hoses, etc. It ran horribly and belched black smoke and bucked violently upon deceleration. Vacuum hoses were missing and the feed back carburetor was not functioning properly. Well, that was my starting point...sorry it took so long.

All of the figures that will be provided are with me as the driver, driving the same route to work with similar weekend driving experiences. I live in a rural area, but have many stop signs while in town. None of these figures reflect highway only driving [those have been excluded].

Initial MPG = 10.41 [2 tanks]

Replaced carb with non-feed back model, removed EGR and air pump, and replaced all normal tuneup components and mileage increased to 15.64 mpg, but with frequent pinging. Thanks to FTE, I learned about Duraspark 2 ignition.

Duraspark 2 ignition installed with timing set at 10 degrees BTDC. It felt sluggish and mileage dropped to 14.10.

Adjusted timing and carburetor using a vacuum gauge [thanks again FTE]. At idle, the vacuum was 21 inches Hg. The truck ran better, but began to ping. After adjusting the vacuum to 19.5, the pinging ceased, performance was better and mileage averaged 15.67.

Even though the air filter was not filthy, I installed a Purelator and the next few tanks averaged 16.08.

In March of this year, a MSD box became available. It was installed without adjusting the plug gap [will be done soon] and the timing was set at 14 degrees BTDC. The mileage averaged 17.26 [13 tanks].

In June, I repaired the A/C [it gets hot in Alabama]. After 11 tanks, the average is 16.85 mpg.

Last week, I changed the transmission grease to synthetic and will monitor what effect, if any, this has. The effort to change gears has been sinificantly decreased.

I hope this information is helpful to someone. I have learned a great deal from reading[listening] to you more experienced members. Thanks!

My 300 six & auto in my van usually does 18-20 on the highway depending if I have the a/c on (Kentucky gets purtee bad too !)
But, I have a fuel economy gauge to help and I drive like what I am (an old fart)

I got 12.4 today '96 4wd. Probably half that was pulling an empty 6X10 dump trailer. Pulled a 12 foot enclosed 250 miles and got about 11. I have not measured it since we got the dump trailer loaded. Been hauling gravel through the hills. Probably not far off from the 12 because I drive it very carefully and slow.

I do know this much. If you let it sit around doing much idling it will really drop the mileage. Seems like mine uses about as much gas sitting at idle as it does moving.

I figured I should add in my truck, although its an F250.

1987 F250 'custom' (no options, not even a tape deck).
326,000 miles
4.9L EFI L6
4.10:1 10.25" axle
2WD
265R75 tires, bald from having 1.5" of toe-out

runs rough at idle, backfires constantly when deaccelerating, exhaust reeks of gas fumes worse than a lawnmower. It's slow, it sounds like a tractor, it pauses and takes 2+ seconds to process when you stomp on the gas pedal....Its well aged.

Unloaded:
Spending 2 hours in stop-and-go traffic brings me to about 11-12mpg. Highway driving, non-stop, for 7 hours @55mph up and down some mild mountain passes averages 14.5-15.5mpg, turning about 2600rpm.

Loaded: I've no idea, $30 worth of gas to do dump-runs all day long, I didnt really care.

with my 93 f150 4.9l 5spd 4x4 126,000. ive averaged 11-14mpg in winter with hubs locked in. summer i averaged 15-16mpg and ive seafoamed it twice and went up north in wisconsin to the pipeline with my spare in the bed and back of my cab filled to the top with camping gear and bed full of wood and i averaged 19mpg on the hwy, this really impressed me.8D now i got 5.0l injectors installed (20#) and im going to try and see what i get now.

last time i checked, i got 16.6 driving 65-75 for 260 miles with my 700+ lbs tool box in the box. Stock everything on it but the smog pump delete and straight pipe after the cat. the 3.08s and 5 speed help. the mpgs used to be better but its just a ranch pickup so it doesnt matter what i get now

'81 F100
300/c6
2.75 rear
225/70R15
4700# GVWR

egr block off, smog removed, straight mechanical advance

around town i avg 14MPG, on the highway 17MPG @ 70MPH / 19MPG @ 60MPH

I have the E40D automatic with a 4.11 gear and 31'' tires all the way around. I get about 16 mpg cruising at 60 mph. I get more than 18 if I follow real close to a wind breaker (like a U-Haul truck or something like that). I don't recomend this, I just found this to be interesting. Shows just how much wind resistance hurt mileage.

81
 

I had a 81 F150 extended cab and long bed 4x4, 300 6, bone stock, stripped down, no a/c, 4 speed trans with granny low.

at 55 on the highway I got 21mpg regularly
at 60 to 65 I got 16 at best

I loved that truck

I just got a 95 reg cab 4x4, I hope it does al least 15 or 16

I have a 94 f150 4.9 automatic extended cab that I've been tuning the ecm here for a couple of weeks. Well I live out in the country so I don't do much interstate driving. I mostly do city driving with a high speed of 55. I did an average the other day of 18.9 city mileage....I might add that I pulled an empty trailer for about 50miles, and I also pulled a loaded trailer (6500lbs.) for 18 miles. I am very pleased with the results so far....Once I get a full tank put on the truck without pulling anything I will let you guys know, but so far so good....My clunker is a keeper now!

i get zero,goose egg, nada! cause she's sittin in the yard, waitin for a motor!:-X16

I have 91 efi how do I delete the smog pump, what size belt, will this effect the motor in agood or bad way The pipe to the exaust is welded shut so the pump is not really doing anything.

With EFI best not delete anything. Rather, make sure everything is working properly including the smog pump.

Get this mine when it ran got 18-20 best with highway, town, gravels
1994 4.9 (Fun1) programed
OBDI
3.55
E40D
LB, RC, 2wd

Dad gets 15-16 best with highway, town and gravel driving
1996 OBDII
3.08
E40D
LB, RC, 2wd

Anyone figure out why this would be?

Your dad has a heavier foot!