I've had my 04 Ranger for about a month now, and I must say I'm extremely disappointed in the gas mileage. Or lack thereof. It is 4x4 with the 4.0 and 265/75 tires, and with all things considered, I expected about 15-17mpg. I'm lucky if I get 12. I cleaned the air filter (its a K&N), checked my tire pressure, and new spark plugs are next on my list, followed by an exhaust. The gas mileage shouldn't be this bad, should it?

 

Well...let's start simple. Fuel filter? Bigger tires=more mass to move. 4x4 equals a loss of MPG. As does the 4.0L for obvious reasons, and automatic tranny if you have it.

You outta get your codes pulled by Autozone or the like, just to see if anything is out of whack. Weird stuff happens. Though you shouldn't be losing sensors by now, just something you could check.

Also, the K&N has a rep for oiling up the MAF sensor in the air intake, good idea to pull and clean it with throttle body cleaner or the like, as foul readings from it can affect your fuel mixture.

RP
Zach

 

If these tires aren't the specified size, & the computer hasn't been corrected for them, then the odometer won't be accurate to calculate the mpg. Speedometer will be off too.

Of course driving style & conditions will affect mpg. If you like to feel the low end grunt of the 4.0L & like to dash stop light, to stop light, & idle a lot in between, then mpg will suffer mghtily.

As has been said, lugging around the extra weight of 4x4, with it's gearing & if it's a auto tranny & super cab, all that = more weight & or slightly less tanny effeciency & mpg suffers.

SO, the 4.0L 4dr super cab 4x4 with it's gearing & auto tranny, with big tires, won't be the queen of mpg!!!!

Now all that said, seems to me you should be getting, or at least be able to get, better mpg than you stated.

I like the suggestion to have the computer scanned for any set or pending trouble codes, maybe they could give a useful clue.

I Also like the MAF sensor cleaning idea, as over oiling those cotton gauze or foam filters can foul the MAF. They'll also pass more dirt & that will help dirty up the MAF too & mess with the A/F ratio as stated.

As has been suggested, be sure to use a sensor safe, non residual solvent to clean the MAF.

Also be sure those tires are aired up properly.

Let us know how it goes.

 

I don't know how much the tires are affecting it, but I have the standard 235/75 and my all-around milage with a 4.0 automatic is 19.8.

 

I'll clean the MAF when I change the plugs. I hope it helps. I wasn't expecting absolutely great mileage, but 12mpg is rediculous.

 

If your going to change the plugs, I'd use the latest specified Motorcaft or Autolite plug & be sure to check their gap. I like to adjust it to the minimun side of spec, as the gap is always opening up.

Make sure your air & fuel filters are changed as specified in your scheduled maintenance call out.

Make sure those tires are properly aired up.

Try different brands of gas. In my area, for the way it's formulated, Chevron or Chevron/Texaco give me the best mpg, in your area, some other brand may work better, you'll just have to try them, keep records & see.

On my 94 3.8L Taurus it's made about 5 mpg difference in around town driving. In my 99 4.0L Ranger only about 2 mpg difference around town & almost 3 mpg highway, along with synthetic 5W-30 oil. The synthetic didn't help the Rangers city mpg so far though.

Just some more ideas for consideration.

 

Yea 12 is way too low, unless your driving it awfully hard from light to light!!! Look the plugs over when they come out to see if it is running too rich (Dark color, and use autolight or motorcraft plugs) Look at the codes and get back to us. Mileage may be the reason the last owner got rid of it, look for any "Modifications" the last owner may have done.
Dave

 

Something is way wrong Im getting over 18 with a 06 FX4 Level II with 4:10 gears 31" off road tires and a automatic with the 4.0. Are you a lead foot?

 

It's not light to light driving, as the town I live in only has 4 lights, and the neighboring town only has one. I used to be a lead foot, when I had a 2wd V8 Dodge, but I've taken it a lot easier on this Ranger because it's not designed to win races. As far as I know, the previous owner did not do any modifications other than a K&N filter and the tires. Hmm... just hit me, maybe I should also have the tires balanced. This sucks, man.

 

Given that these are rated at 15/18 or 15/19 mpg right out of the box, depending on the tranny, I would begin by dumping the KY filter and inspecting the plugs. Is the front end properly aligned? Engine at the correct operating temperature? Are you checking the mileage over, say three tankFULLs rather than just a few 100 mile trips?

Something else to consider, since the 4.0 is prone to engine knock........if the previous owner took it to the dealer complaining about knock the dealer may have flashed the PCM with an end result being that the timing is overly retarded. This will have a dramatic effect on your mileage. So on that note, and assuming you have warranty left, you might schedule a visit to the dealer to express your mileage concerns. You should also be able to call him and run the VIN through OASIS to see the service history of the vehicle.

*Your mileage expectations, provided you're not leadfooting it, are totally reasonable.

**Have you run a number to see how the speedometer/odometer was affected due to the tire size change?

 

One of the weirdest things I've seen with this truck is that I can only go about 120-130 miles on 3/4 tank of gas. Sometimes I can stretch it to 150. Unfortunately, I have two jobs and very little time, and less money to fix the problem. I now have 150 miles left on the warranty, and no time to take it to the dealership until about two weeks, by then the warranty will have expired.

As far as the other things, the frontend is very well alinged, as it has no pulling to any side nomatter what the speed is. The stock tires on this truck were 245/75 r16, and the ones on there now are 265/75, only a fraction of an inch taller.

Thanks for all of your help guys, and when I fix the problem, I will let you know.

 

Sounds like it's running rich, so I'd clean that MAF sensor right away.

There is a link on how to clean the MAF sensor, in the "Technical Information" thread, located atop this forum, lots of other good info located there too, so be sure to have a look see.

 

You got me Dave!!

 

I have a 98' 4.0 4x4 auto, and I only get 12mpg also. I have 3.73 gears and 31x10.5 tires. I had the plugs wires and all 02 sensors changed in fall, and the MPG on the first tank after that was 16mpg, but I haven't equalled that since. I don't get a CEL and it seems to run fine. I don't expect great mileage as I live about a mile from work (I know, I should ride a bicycle), and those short trips will kill the mileage, but it seems that it should do better than that. I like the truck, but with it's poor mileage I'm thinking of selling it.

 

DAVE I have the same truck as you, but with a manual trans, I run synthetic fluids in the engine, trans, t-case, and rear, I also installed a k&n 77 series intake, jba headers, gibson dual sport catback, underdog udp, e-fan, and programer, I also run 265/75-16 BFG's. I get 18 to 19 city, and 22 highway, but when my truck was stock I still got 17 city, and 20 to 21 highway. I don't know why the mpg varies somuch between 4.0 powered rangers, I belong to 3 ranger forums, and there are others with the same complant, then there are those who get mpg simular to mine. Even when I run the dog water out of mine, 16 is about the worst that I get. 12 seems way to low, something doesn't sound right. Call your ford dealer tell them of your problem, and make an appointment, let them know your warrenty will expire before you get in, so they have a record of it, they should still honor the warrenty. Good luck!