2005 V8 Mountaineer Mileage Problem

[shoot25]

I purchased my 2005 Mountaineer V8 in 2007 with 22,000 mi. For the first year or so, I checked the fuel mileage with every fill-up and was getting 14.5 mpg around town and 21 mpg on highway trips. I noticed last fall that it was dropping and began checking it again. I am now getting 9.5 mpg around town and 15.5 mpg on highway trips. I had one dealer tell me it was the fuel and they said that since it was not tripping any codes that there was nothing they could do. Another Ford dealer ran a complete driving test and said that I needed an MAF sensor and one coil on cyl. #8. These were replaced under warranty, but I have noticed no improvement in the last eight weeks. I still show no check engine light or any other problems. The vehicle has always seemed to run fine with no miss or hesitation whatsoever. I really love the vehicle otherwise, but the mileage is killing me. Any ideas?

 

[my pos mounty]

You do not list where you live. Up here in New England (is this reformulation nationwide?? I dunno), they actually reformulate gasoline to a "winter blend" which decreases our fuel economy, but is supposed to be better for the environment and Al Gore.
Also, keep in mind the newer ethanol/gasoline blended gasoline yields a little lower fuel economy as well, for the same reasons as stated above. So, higher gasoline prices for gasoline that is formulated to yield less miles per gallon.
While your "around town" mileage seems a tad low, your highway sounds right for the V8.

 

[shoot25]

If I were talking about 1-2 mpg less, I might buy that the change in gas formulations here in Pittsbugh, PA may be the culprit. But I am looking at 1/3 less mileage than what I know what I was getting for at least a year's worth of driving and about the first 10,000 miles I put on the vehicle since I purchased it. The car only has 42,000 miles on it now.

In case it helps, I have checked for fuel leaks, sticking brakes, and the transmission seems to shift just fine. Also, I owned a 1995 Town Car with a 4.6L V8 for several years. I consistently got 15 mpg around town and 24 mpg on the highway. While I would expect slightly less with AWD, I believe that it should be in the same ballpark.

 

[FordmoPar69]

one thing that you could do is make sure that there is nothing blocking the intake tube. and depending on the milage could also be the torque converter or bad tranny fluid. (always use the good fluid when dealing with fords, ive found that the like the motorcraft or valvoline full synthetics). and being awd, change the transfer case fluid.

 

[FordmoPar69]

also to, if the bearings and diffs havent been serviced, do it before 70,000mi if not sooner, if your past that do it now before major damaged and expensives repaires are needed

 

[Merc02]

I'm sure you're on to the regular stuff, like new plugs(use OEM Motorcraft, not fancy performance plugs), air filter, fuel filter, tire pressure.

Maybe its where you get your gas. You could be consistently getting poor gas at your favorite spot. Try newer reputable places rather than generic corner stores. If you already use a reputable place, then try another place. You shouldn't need higher octane than 87, but the higher grades will give you better mileage (Not 1/3 better though).

Some people use higher temperature thermostats to run the engine hotter to fool the computer to run leaner. Maybe the colder temps where you are are having the opposite effect???

 

[skeeter123]

Yes, alcohol has less energy per gallon than gas; so when they put 10% alcohol in they're not helping your mpg.
Also, the upstream O2 sensors have a lot to do with your gas mileage. 42K is early for O2sensor probs, but they can go bad gradually w/o throwing a code, just reducing your mpg.
If you have a scanner you could look at the live data for O2 sensor performance, and fuel trim.