I have a 92 5.0 f150 4x4. i get 12 on the highway at best. just did complete tune up and no increase in mileage.. truck only has 31in tires with 3.55 gears i think that i should get better than 12, any ideas what i might have missed""

 

Have you recalibrated the speedo for the tires? If not you're going further and travelling faster than you think. If you have a mechanical speedo you will have to change the speedo drive gear where the cable attaches to the tranny, if it's electronic then you reprogram the PSOM. Do a search for more info on both.

Just about everything affects milage so make sure there are no codes and that you don't have the fuel transfer problem if you have dual tanks.

 

31's on my old 4x4 Ranger threw the odometer off by 14% slow and the speedo read 10mph slow at 60 mph,.........Do what Conanski says, and you will find you mpgs are better than you think.

 

speedo is dead on had some one pace me and and checked it with radar..(uncle is a cop) no codes thrown and i dont have the tank problem. just not sure what else i could be. i c alot of ppl on here get better milage just not sure what the deal is

 

Check the odometer readings against GPS or the odometer check section on the freeway(if you have one nearby)..........Bet if you go thru a 1 mile section, your odometer only reads 8 or 9/10ths of a mile.........Speedo can be dead on and odometer be wrong.

 

yea good point never thought of that ill check it tommorow

 

is my truck OBD 1

 

Yes,................Be sure to check mpg over a full tankful and a full refill......No use guessing!.

 

I changed from 235/75 x 15 to 31 inch tires and it is easy to lose 1 to 1 1/2 MPG.The 31 inchers weigh 10 pounds more per tire and act like heavier flywheels--harder to accelerate-and stop.Rotating weight has the same effect on vehicle performance as 10 times the same mass of non rotating weight on a vehicle.40 pounds of rotating weight= 400 pounds of non rotating weight.And the tire structure can also increase the rolling resistance of the tire. 31 inch tires will never have the low rolling resistance of P series street tires. This has an effect on acceleration and MPG. Especially if the tires are not aired up -I keep mine at 38-39 PSI.

I would suggest checking the calibration of the speedo/odometer. Yours is electronic on your 92. Click on this:

https://www.ford-trucks.com/article/...ND_BRONCO.html

What kind of transmission do you have?? If it is manual overdrive and not the T18---it is very possible that how the manual is shifted can cause lower MPG. The 3.55s are slightly ungeared for 31 inch tires-especially if the transmission is a manual. Hilly terrain and high overall gearing could cause low MPG.

And if the oxygen sensor is more than 50k miles old-I would suggest replacing it. My 100k mile oxygen sensor caused a loss of 1 1/2 MPG average on my 302/5sp/4.10/4x4.

 

the truck has a E4OD in it

 

Check the calibration of the odometer and the oxygen sensor. But --do you realize that 12 MPG combined city/hwy is real close to what the EPA rated this truck when it was new??

 

i'm hoping that it was an oxygen sensor in my truck that lowered mieage. before i changed them i was getting 120 miles on a full front tank. now i'm getting 85 miles on just 1/2 tank. i'm keeping an eye on it I hope it stays that way.

 

BTW.. the fuel gauge cannot be used to calculate accurate milage. After filling the tank reset the trip meter and drive as usual. When you refill again record the amount of fuel pumped and the distance traveled, that's your milage. It doesn't even matter if you run the tank empty or not, it's still an accurate milage snapshot. Average the numbers obtained over several tankfulls and you'll have a pretty good idea of the real fuel consumption. Of course the odometer and speedo have to be dead on and a portable GPS is probably the best way to calibrate it, I had to make a speedo recalibration when going from the stock tires to 31's.