I have a 1989 f150 with the 300 i6 with a 5 speed and I was wondering what can I do to increase mileage?

 

Increase it from what? If you're getting 15-18mpg combined city/hwy then that's about as good as it gets, but if it's significantly less than that you have problems to fix.

 

I'm with Paul above. The only thing that you can do with a well-tuned truck is to drive slower and use less go pedal when accelerating. You could draft semis all day, but I wouldn't advise it.

 

start with adjusting the nut behind the wheel.then focus on aerodymanic improvements.nothing else will come close to gains seen here.
start by searching here Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com
start with the two links called: 65+ Efficiency Mods & 100+ Hypermiling Tips towards the top of the page.
then search there for more on these keywords;
front air dam
underbelly pan
aero truck cap

 

Dittos to all of the forgoing. What axle ratio does your truck have? If a 3.55 (code 19 or H9) you could pick up a few additional MPGs by swapping in a 2.73 (code 12) or 3.08 (code 18).

dn.

 

Yea 20 mpg is as good as ive been able to get

 

My 94 F150 with 300/5 speed had 3.08 in axle. average was 18 in strict city miles and hwy 21-22 mpg

 

I am in the process of prepping a 2.73 axle for my brother-in-law's 94 F150, 300-6 with M5OD per his request since I have driven it some myself and, with its stock 3.55 rear axle, it only does about 10-12 MPG in combined driving. Since he does not need it for towing or load capacity but just as a light duty runner this is the perfect change.

dn.

 

If he getting 10-12 mpg there are definably issue with engine. My 2 trucks get 16-20 with 3.55

fix engine first then check mpg before swap rear axle.

 

That's music to my ears!!!

 

Yep 16/20 for me to 4x4 with 3.55

 

try a front air dam. i bet you see at least 21 if not 22 hwy on your first tank.

 

I was getting 25 highway with my 91 f150 2wd and 22 city before the head gasket went out. 77k miles though with 2.73 gears.

 

i get 21mpg all day long on the highway and i do 70-75mph and get about 17city. i eliminated the egr and smog pump. and the fan clutch went out so i decided to put an efan in it. 300 6 m5od and 3.08 gears.

 

I forgot to mention, I got rid of my ax pump when it blew out, installed a custom cold air intake, and believe in oil changes, tranny flushes, rear end fluid changes every 2k miles. I'm sort of OCD with my truck.