I consistently get 12 mpg with 50/50 highway/town driving. I get worse economy when I drive the truck super easy, I might get better economy driving her moderately hard, and I'll get worse economy pulling out at WOT everywhere but still better than driving easy. I gained 1 mpg from installing an electric fan. I lost 1 mpg when I lifted 3.5" which was unexpected. So far, exhaust and intake modifications including cam/lifters/port and polish have made no mileage difference what so ever, only power differences. I lost ~.5 mpg when I went to 265/65r18 Cooper AT3s vs my 255/65r16 Capitol Precision Trac IIs. I run NGK spark plugs, but I can't remember exactly which ones. I might pull one later to check, I need to check them anyway. My truck has 142k miles, automatic transmission, stock gears. I currently run Rotella 15w40 oil and 85w140 gear oil. I have previously run 15w40 Royal Purple, no mileage change. I have a light brush guard on the front, probably about 50-60lbs. The truck runs the factory 190 stat (short term) and I have a hi-lift mounted on one of the roof rails. I keep probably 400 lbs worth of tools and stuff in the back hatch area and I have a 5 seater truck. I also did an A/C delete, mileage changes were inconclusive. Oh, and all new O2 sensors, but still on the factory MAF (unless it was changed by the PO) and I have a minor pre-O2 exhaust leak, but enough to throw a code. Runs a little rich. To be fixed with headers and all new exhaust because the factory manifold to y-pipe gaskets keep leaking.

As stated, I consistently get 12 mpg whether I am doing town or highway driving, and shockingly whether I am towing or not.

I have heard of guys consistently getting 15, my truck didn't get that when it was all stock. I've also heard a few guys say that they get 17-19 which I find insane, but believable because I somehow got 19 on ONE tank, and I've never been able to replicate it.

So, I'd love to hear from anyone and everyone! Give us a huge info dump on your truck. Lift, plugs, sensor age, mods, tire size, 4.6 vs 4.0, intake, exhaust, etc. Post everything you can think of and what mileage you get, as well as what changed your mileage if you know. I'm not all about hyper-miling, but there's such a large gap between what some people get and what others get that there's got to be a way to squeeze a few more MPGs out of my daily driver.

Thanks guys!

Doing an edit because it was brought to my attention I didn't mention gasoline. I exclusively use Shell 93 octane and my mileage calculations are accounting for the larger tire size. Also I have STI 8mm plug wires.

 

The one thing you didn't mention is what type fuel you use.

I recently did a 1200 mile trip and noted 15.6 all freeway 75mph half the way and 65 on two lane the rest of the way. On one 300 mile leg of that trip I ran Costco Supreme 92 octane 10% ethanol. 15.6 mpg. On that same leg reverse direction running Chevron supreme zero ethanol and one can seafoam (because the Costco gas gave noticeably weaker response) i got 17.6!!

The 17.6 was also entirely on 200 miles of that leg that were 60mph speed limit two lane highway.

Then on a recent freeway trip, Chevron supreme 10% ethanol, 75mph, back to 15.6 mpg.

My thought is freeway speeds of 75-80 mph which is 2800+ RPM as well as ethanol in the gas could lead to less mpg.

 

Most of my driving is around town driving. Not much over 40 MPH.

UltraGauge says 9.07 MPG.

Lift: TF MD Springes w/ 2" SLS spacers
Tires: 255/70R18 Hankook DynaPro ATM
4.0 w/ Crower 229 cam
TF Sliders

I also have 85w140 oil in the transfer case and diffs. I am sure the higher viscosity affects MPG in a negative way.

 

My mpg is super high, I dont know why.
I always use Shell gas.
5W30 con. oil, if I am not mistaken.
It shows around 22mpg on highway if the ac is off and I dont go over 60mph! Everything is stock + a metal brush guard.
it goes as low as 3-4mpg if I 'drag race' from a complete stop.

 

How are people reading mpg?

Only decent way is to divide number of actual miles travelled, by number of actual gallons it took to get you that far.

Any other electronic wizardry is going to be less accurate and so misleading in any kind of poll/study/thread thingy.

I usually do between 12-12.5.

 

I have a bluetooth obdII reader and torque app on my phone.
i checked the device on 2 vehicles ( Crossfire and a Rio)by waiting until the gas light comes on, adding 10$ gas and drive it until the light comes back on.
and what i calculated was super close to what it said. So I assumed what it says for dII is going to be correct also. Maybe I should calculate it the old school way to make sure. 22 should be impossible with this machine.

 

The instrument cluster mileage will be incorrect with tires that are a different size form stock.

You can calibrate the UltraGauge to correct mileage. You need a road with mile markers. You go X miles and compare it to the UltraGauge, then adjust/calibrate the UltraGauge. Then future mileage/MPH reading will be correct. The MPG is close on my UltraGauge based upon the gallons it takes to fill my tank vs. what the UltraGauge says is remaining.

 

17-19 on the highway 15 mpg around town 87 octane DII

15-17 on the highway 11-12 mpg around town 87 octane 1983 110

 

I edited to include that I exclusively use Shell 93 octane and my calculations are done using the trip counter divided by gallons and accounted for the larger tires.

What kind of spark plugs and wires are you guys running who are getting 15+?

I might have to try a tank of no ethanol.

 

Between 15-19 on the highway for all three, depends on which way the wind is coming from. The 4.0 gets a little better in town. RR probably gets the best overall on the highway, but it is also the lightest of the bunch. 89 octane.