Excessive poor in town mileage

[ironmountain]

I have a 99 Mountaineer AWD, 5.0. 120,000K. Recently it had a rather sudden drop in in-town mileage, from average 14-15mpg to 9-10mpg! No codes and no check engine light. I have changed the Fuel filter, Air filter, Plugs and Wires. The Hywy mileage is still good..around 19mpg. No leaks or fuel smells.

Does anyone have any ideas what could cause this that does not code? Any help is appreciated. THANKS!!

 

[SoNic67]

Got colder recently? Check the tire pressure.
Highway trips tend to be longer duration, higher speeds, heating more the air in tires - higher pressure.

 

[Jason c]

Must be something in the gas. Mine has gone down hill the last month or so too. I have changed just about everything related to fuel economy and it is still low.

 

[koda2000]

have you ever replaced your O2 sensors? at 120K they're due to be changed and can explain your poor fuel milage. try running a finger inside your tail pipe. if you find black soot, you're running too rich (as in much fuel) and this condition will not necessarily throw a code.

 

[sport97]

Winter blend gas lowers MPG's. I had a 2-3mpg drop off as well. I was going to do new o2's but ill check my mileage in the spring first.

 

[1996BLKBauer]

19 MPG Highway? I maybe get 15, in city it is 9-11mpg. Although, my truck is way over due for some repairs. just waiting on spring to get here so i can get to work.

Also I hate this summer/ winter gas crap. One year winter gas is more expensive to make, then the next year summer gas is more to make. It seems like a bunch of crap so they can charge more for it. I am only 20, but my dad does not remember this gas changing with seasons stuff going on until recently.