So I have an 84 Ford f150 4x4 with a 300 inline 6 and a 4 speed and it has 3.55 gears. It's a Single cab short bed. So my question is, what's the best easiest way to get better fuel mileage on it, it gets about 9 miles to the gallon and I want it to be a little better.
what is the mileage please?
You're driving an old, inefficient (probably TBI), heavy, 4x4 truck
If you're worried about fuel economy, then you've driving the wrong vehicle.
Here are some Scotty videos:
https://www.youtube.com/c/ScottyKilmermechanic/search?query=fuel%20economy
Your best bet is going to be to change your driving style..
If you are looking at the little AutoZone bottles they all be snake oils. Not much to do buddy. It's a 84 truck. If you want to save even a drop of gas, ya gonna have to start tearing it apart. Lighter load=save more gas to an extent. Also depends on how you drive I guess.