Im noticing my mpg dropping in the past couple of months. I usually get 19 or 20 in town, and up to 23 on the highway. Now im lucking if I get 16 or 17mpg.

I have a 2001 escape XLT. 6cyl 4x4.

I changed the spark plugs, coils and fuel filter about 3 years ago (almost 40k miles ago).

The car starts fine, seems to idle fine, seems to accelerate ok. The only thing that is off is the MPG.

I dont just want to throw money at parts. Which one should I replace?

 

Replace your gas station first, perhaps. It might just be the particular fuel you've been buying, especially if you usually got the same place. If you're in any of the areas where the EPA requires special summer-time fuel blends or elevated ethanol levels, be aware that those can also kill your fuel economy (as can a large number of other things...).

Start with basic maintenance: Tire pressure, air filter, driving habits, check for brakes hanging, etc. Log your mileage so you actually KNOW what your fuel economy is running at.

 

Try a tank or two without any corn squeezins. The stuff is blended in at the pump itself I guess. It can run higher than 10% concentration and will really send the mpg down. Might be tough to find "pure" gas in Neb. but try it and see if the mileage doesn't come back up.

http://www.pure-gas.org

 

Its hard to find gas here without ethanol, but its always 10% ethanol. Its the same stuff from the same gas station Ive used for the past 3 years. I did the calculation, Im getting 14mpg, this is combined city/highway, but I would think that number would lean more highway as I dont really run into many lights. I would usually get around 19mpg during the warmer months for combined driving. thats a full 5mpg drop!

 

The alcohol is blended in at the refinery or distribution point. It is not done at the station as they do not have separate tanks for it.
Some companies add extra as it is/was cheaper than actual gasoline.

You can test for the alcohol content with simple chemicals. Taking a fuel sample, and adding water, I think, and noting the measured volume change can indicate how much alcohol is present. If the refiner is adding more than the 10% allowed, you'll get worse mileage. You should not blame the retail station where you bought the fuel as they have no control.
Search for how to test the ethanol percent, and measure. Other than that, get a scan tool and watch what the engine control system is doing, noting if things are amiss. A lazy thermostat can affect mileage, and you'd likely not notice a dang thing in the summertime as you would in winter when the heater didn't work so well. Get a non-contact thermometer and read the temperature at the thermostat housing hose leading to the radiator.
tom

 

Here's a handy way: