Just bought a 97 F150, regular cab, short bed, 4*4 4.2 with 102000
miles. I'm getting about 14-16 miles to the gallon, highway.
Ran a code test, passed.
Changed spark plugs, no change.
Justed check the voltage to the driver's side bank 2 O2 sensor. Voltage was 14.5 volts. I would only receive voltage to the O2's after the computer went to closed loop, correct?
Going to check voltage to the O2's when cold, should be none, and I'm going to check the voltage, that the O2 puts out.
What's the deal? I talk to a guy who has the same truck as mine, but a 98, and he's getting about 16-18 miles the gallon in town. I thought I would get at least 20-22. Any ideals?
Thanks Chad.

 

I just sold a 99 4x2, 5spd, 4.2L. The best I ever got was 18, and that was highway driving with speeds around 64 (Kansas Highways). Around town I would get around 15-16, never better. This was never towing or with a lot of payload. I expected to get better milage. After 20K the milege improved to the numbers I stated, before that it was worse. I also have a light foot, believing how they are driven reflects how long they last. What tranny do you have? Also must remember 4x4 is heavier=more weight for engine to move. What gears do you have? I enjoyed the truck. It definatley served its purpose. I bought the 02 for the extended cap, 4x4, and I need it to towe on occasions. I never had any trouble with the 4.2, and my only complaint was the mileage. I tried everything I could think, but as long as it stayed constant, and didn't ge worse, I figured things were working correctly, and that Ford just wan't as accurate with the estimated mileage per gallon. Good Luck, Levi

02 F150 4x4 5.4 V8, 3.55 limited slip, sport.

 

Also just bought 97 F150 reg. cab 2WD w/ 4.2. My first tank I got 16 mpg. Just filled up the 2nd time, 15 mpg this time. I have 88K miles. Not great milage, but I'd rather get 15-16 in a truck than 18-20 in a Buick (what I was driving).

Keopf

 

Those numbers don't sound too much off. Are you sure that pal of yours is truthful / not too optimistic with his math? I can tell you, you will NEVER get 22 mpg on yor truck. Just ain't going to happen. These trucks are pretty bulky (air resistance) and quite heavy too. That is just limiting what you can expect from your gas mileage. My friend has the 4.2 and it sure seems to take about as much gas as my 4.6. Put anything behind it and you will be in the single digit!

Gas is cheap! :_)

Cheers, George

 

I have a 97 F-150 4X2 4.2L and was getting about the same thing. I've recently gone on a improve-my-milage kick. I almost hesitate to say this, do to the heated response this topic often draws, but I installed a K & N air filter to see what happend. On the first tank of gas after installing the filter I logged a 1 mpg increase, and thats in city driving. Durring subsequent fill-ups I never get less than 15mpg any more and often get over 16.5 - 17.0 Not a big increase, but some. I haven't done enough highway driving to determine my increase there, but based on my city results I expect 17.5 to 18. I thing 18 mpg is a fair number for this size of truck. I also noticed a SLIGHT increase in HP when accelerating from a stop, and a significant increase in available power in 5th gear. I think a K&N is a good investment as long as you have reasonable expectations. It won't turn your truck into a sports car, but for $60 bucks why not?

I'm now considering a Flowmaster exhaust to try and drive up the city mpg some more. I may go get one this weekend.

 

You are getting about the normal gas milage for the truck with that engine as other people have pointed out. Regarding Your O2 questions with 102000 miles on them it couldnt hurt to replace them (which is harder than it looks. they wont like comming out). You are right that they only function in closed loop mode. You cant get an accurate test with just a multimeter. You need a graphing multimeter or oscilliscope to view the wave patterns the sensor makes. It is not just the change in voltage that is important it is the rate of change which needs to be seen on a graph. Obviously because no codes are found on your truck the sensor is functioning and giving the correct output voltage it just may be lazy because it is old.