I have a 1983 F150 W/300 I6 engine. It is in good shape and seems to run well. I just had the carb worked on (gaskets replaced, other parts replaced). I drive the vehicle in town mainly for short distances. I'm only getting about 10 MPG. Is this normal? I'm sure it will do somewhat better on the hiway. What is a reasonable expectation for fuel economy for this vehicle?

 

Well that depends on what type of transmission, gears you are running in the rear end, if you have a 4x4, and what size tires you have for starters. Lift kits etc...

My 1981 F-150 2wd, T-18 4 speed, 2.75 gears, P-225-75-R15 tires, averages 21 MPG.

I would say in my opinion, that there is probably something wrong if it gets below 15 MPG, unless you are running extremely low gears with a lift or something. But need mre information,

 

I have a 4-speed tranny (not sure which one) and the vehicle is 2wd. I am running 225/75/15 tires. Anyway to ID which tranny I have? How can I improve MPG?

 

On the vehicle saftey certificate lable, there is a transmission code, and a axle code. I or somebody else should be able to decode it for you and tell you what tranny, and axle ratio you have.

You said you, or sombody worked on the carb. Was it a rebuild? Was the fuel mixture set right?

Any vacuum leaks around the carb, or anywhere else. Brake booster, vac lines etc?

If you have a Duraspark II ignition system. (ignition module located on the fender), have it tested at the local auto parts store. Could have a "running" fault in the module. Check the workings inside the distributor. The magnetic pickup, the vacuum advance. Check for wear in the moving parts. Check to see if you have vacuum advance by hooking temporarily to manifold vacuum. Should change timing, if it doesn't replace it. etc...

Replace the O2 sensor, should replace it when you do a tune up.

Check EGR valve operation. A good EGR can save you gas. A bad one can suck your tank dry. Is the valve leaking vacuum? etc...

Clutch slipping? Wheel alignment, tire pressure, shocks, etc... all can have an effect on gas MPG.

It could just be one of these things or a bunch of these things together adding up.

 

While the 300 isn't particularly efficient to begin with, 10mpg is not normal. I would think that some carb work was done wrong. My 94' 300FI sees about 16 in town and 19 on the highway.

 

Mileage? lol, I've an 83' 4x4 F250, 3.55 gears c-6, 35 in tires, and I get 11, uphill, downill, loaded, empty, city, highway, 11... until I lock in the hubs... then I get 5-6...

but a 300 6? should do better...

 

I don't know. If your city driving includes lots of stoplights, warmups, etc....ten may be realistic. My 300 gets 20 on a strictly highway trip, but 12 doing ranch work....lots of idling.

 

My driving is short trips (2-3 miles). The truck doesn't get warmed up much.

My tranny code is A
Axle code is 18
What tranny and gear ratio do I have?

 

One other question, do I have an oxygen sensor? I have a carbed engine with no computer so I did not think I had an O2 sensor. Also, the EGR valve is new.

 

A is 4 speed New Process (not overdrive)
18 is a 3.08, sorta middle of the road.
No O2.

 

Thanks for all the info.

 

With the information given, My opinion, and it's just my opinion, the truck should get around 15 MPG on average, with swings of 18 MPG, to 12 MPG depending how it's driven, etc...

Each 300 engine (or any class engine for that matter) has it's own "Personality", and mileage will be affected by it's "Personality".

10 MPG may be the best you can do, but I'd check some things to make sure it is the best before giving up.

 

I just did about 90 hiway miles. I am guessing I have a 16 gallon tank(?). I figure I used about 6 gallons of gas. That puts me at about 15 MGP/hiway. I would be happy with 18. 10 in town is unacceptable with today's gas prices. I will try setting the timing up a hair and check vaccuum lines to see if that improves anything. Short of that, ole blue gets parked for a while or sold.

 

You needn't guestimate.
Do you know how to calculate it precisely?

 

how much do O2 sensors usually run?