06 4.0 mileage issues

Superlifted06FX4 · #1 11-28-2009, 11:28 AM

I drive an 06 FX4 with the 4.0SOHC, 5 speed auto, stock 4.10's. The only changes from stock are a T-bar crank, airbox mod, exhaust and 32x11.50's. I'm getting approx 14.04 mpg mix driving. I'm confused since it seems like I got the same mileage on my stock 31's. If someone else wants to do the calculations, be my guest. Trip odo says 229.1 miles and I put 16.312 gallons in. What am I doing wrong, it should be better, shouldn't it?

STL · #2 11-28-2009, 11:34 AM

is it all city, all highway or mixed

if it is mixed that is about what I get with mixed driving

Ever change your fuel filter?

Tom · #3 11-28-2009, 11:37 AM

Quote:

Originally Posted by Superlifted06FX4

I drive an 06 FX4 with the 4.0SOHC, 5 speed auto, stock 4.10's. The only changes from stock are a T-bar crank, airbox mod, exhaust and 32x11.50's. I'm getting approx 14.04 mpg mix driving. I'm confused since it seems like I got the same mileage on my stock 31's. If someone else wants to do the calculations, be my guest. Trip odo says 229.1 miles and I put 16.312 gallons in. What am I doing wrong, it should be better, shouldn't it?

So you're getting the same mileage after your bigger tires and you think that's a problem?

16 MPG for a 4x4 4.0 w/ 32s sounds about right.

Jay FX4 · #4 11-28-2009, 12:13 PM

Quote:

Originally Posted by Tom

So you're getting the same mileage after your bigger tires and you think that's a problem?

That's what I was going to say. If anything, be happy that putting bigger tires on didn't make your MPG go down. Why would you think your mileage would improve?

Maybe if you did strictly highway driving, you'd see a small increase,
but if anything, getting the bigger diameter tires turning (not to mention the increased rolling resistance of increased width) usually makes MPG go down.

surfer03133 · #5 11-28-2009, 12:58 PM

did you recalibrate your speedo after getting bigger tires?

Fx4wannabe01 · #6 11-28-2009, 01:03 PM

That there trip odometer reading is probably off........

I saw my best numbers with the 4.10's and 32's. Of course I've got a 5spd manual...so idk if that makes a difference or not.

I like my 19mpg after a short road trip. hehe. Not bad for a big truck on 5's!

Superlifted06FX4 · #7 11-28-2009, 02:09 PM

Tell me how to get the filter off, I ain't seen this style connector before.

Superlifted06FX4 · #8 11-28-2009, 02:10 PM

Quote:

Originally Posted by STL

is it all city, all highway or mixed

if it is mixed that is about what I get with mixed driving

Ever change your fuel filter?

Mixed. I expected a lil better, not much, but a lil.

DisturbedESV · #9 11-28-2009, 02:17 PM

Are you accounting for the size difference in tires? I mean, my tires are 13% bigger than my stock ones so my odometer reads 13% lower than where it should...

Say your tires are 8% bigger than stock... you actually traveled 247.428 miles and that comes to 15.168 MPG. Also depends on how you drive. I have a 4.0 V6 4x4 5 Speed w/ 33s on 3.73 and I get about 16-17... that's anywhere from 50/50 city/freeway to 100% freeway... I don't ever break 18 anymore. Your engine is 2 years older than mine but I'm not really surprised at your mileage. Changing your driving habits might help but I think you're right where you should be...

surfer03133 · #10 11-28-2009, 02:22 PM

if you didnt recalibrate your odo after changing tires, you'll need to multiply the miles by 1.03257329, that'll give your exact miles. for 229.1 miles-- it would be 236.5 miles actual, not much but it improved your 14.04 mpg to 14.5 mpg.
^thats only if you did not redo your odo

Superlifted06FX4 · #11 11-28-2009, 06:06 PM

I had Ford reset it. And my truck only has 40k on it.

Superlifted06FX4 · #12 12-03-2009, 01:32 AM

Well this week I got 16.1 mpg after corrections. I still need to do the air filter and the fuel filter, and I already changed all the fluids except the oil, its not due yet. Tires are at 45 psi, and I doubt it needs plugs and wires at 40,000 miles.

Jay FX4 · #13 12-03-2009, 07:30 AM

What are you expectations?

While it is possible to get better mileage than that, 16 mpg is still better than it's EPA city rating.

RoadDawg · #14 12-03-2009, 09:47 AM

For the real deal on your calculations click on the link below and use the tire size calculator... Enter your original tire size into the field at the top and the new size into the field/s below... then click compare. The data will come back and it will tell you every thing you need about the variation in size measurements, speedometer difference, width/height and diameter difference etc...

BTW My mileage is running around 17-19 mpg over all combined average.

CLICK HERE > http://www.1010tires.com/tiresizecalculator.asp

dixie_boysles · #15 12-03-2009, 09:54 AM

going from 31 to 32s, would it change the speedo much? if so by how much?