I have a 97 4.2L V6 2WD F150. I am barely getting 10 miles to the gallon. If I stretch it I'll get 250 miles to the tank. Which obviously leads to only 10 mpg. I drive 1/2 highway, 1/2 city. I have a K&N air filter and 20" rims. I also have a hard top cover on top of the bed. The truck has 117,000 miles on it.

Is this it? Or could there be something wrong? BTW there is no visible leaks from under the truck.

 

Do a tune up. Plugs, wires, coil packs, and filters. How hard do you drive it? Any check engine lights?

 

I'm thinking maybe because your 20" rims may have thrown your odometer off and it's obviously not reading proper. It's just a thaught, otherwise try doing a major tune up, with over 100k it may need some stuff, but usually these trucks can score at least 17 mixed so WTF?

 

I drive it pretty easy. On the highway I'll drive about 65-70. I never gun it or dog it. No check engine light.

As for the 20" rims. When I got the truck I noticed it was pretty bad. I then switched to the K&N filter thinking that would help. But it didn't do a thing....

 

Do everything I listed above, and get your speedo corrected for the bigger rims and tires, assuming they are bigger.

 

Go down a couple of dirt roads and you'll see what it does. You'll be taking a can of ether to your IAC valve and MAF sensor!