ok best i've gotten was 270 from a tank, 18 gallon tank, 4.0, 3.55, auto.. meaning about 15mpg.. but heres my question.. i didn't recalibrate the odo after adding my 31's.. so what do ya'll think i'm realling getting? i'm guessing the most difference it could be was like 30 miles.. that might be overshooting it a little but just a guess from me.. so that would mean like 16.6.. but what do ya'll guess i could be really getting??

summary(in case you got lost): 15 mpg now w/o recalib. 270 mpt. what am i really gettin.

 

when i went from my stock tires to 31s i figured they were about 10% off stock. i did this by using the mile markers on the road and compare to my odometer. when i reached 1 mi on the odometer i really went .9 mi on the road (if i remember correctly, been a while). im sure youll get similar results so your guess of 16.6 from the 15 is probably pretty close to the actual mpg.

 

Try dividing the height of the new tires by the height of the stock tires. My goodyear rts tires were 28.5 inch new, and my 32's were actually 31.5 inch. They cheat , but what can you do? I think your new tires are probably 7% bigger than stock. 15 X 1.07 would be 16.05, give or take.

 

hm so 15 or 16, guess thats not too horribly bad, my trucks due for a tune up anyways

 

im still getting 14.47mpg highway and even worse in the city. thats unacceptable.

 

well if you haven't adjusted your odometer then you're in the same boat as me. and might be getting bout the same gas mileage

 

I usually just add 15 miles every tank to figure mine out.
I went from stock to 33's

 

I went from 245/75r16 to 265/75r16. thats 8% difference. However what you may
not realize is factory speedo/odo's can be off by 2mph@70mph or more.

Now when I'm doing 70 on the speedo my gps says 70.9mph
Also had a friend clock me.. and its within 1mph now..
makes you wonder how much you get jipped on your warrenty..
i mean if it was off that much it was off over 1000miles at 36000...(with stock tires)

So the point is.. You cant just check with old tire /new tire
Just get a gps, go on a nice straight road set the cruise at say 65.. and see what the gps says.
Another way would be to set the cruise at 60mph(for simplicity)
then go time yourself with a stop watch for 5 mile markers or so
I say 5mi to lower the chance of error/make it more precise.

Rand

Btw miles per tank means absolutely nothing.
Leaving off the fact that there are 2 different size gas tanks..
Figure out your MPG.
Total miles traveled/total gallons over 2-3 fillups and you will be alot
more accurate. 200 miles per tank could be 10mpg or 30mpg depending on how much you filled your tank with.

 

i got 33s now and get bout 250 on each tank but i baby my truck :)

 

ur probably getting about 19-20 mpg....wait thats me......hahaha 3.0 is sounding better than urs right now isnt it bossman.

 

3.0 nice, but I got the 4.0 4wd. Im not gettin 19-20, im gettin at least 20(hwy) and at least 17(city) LOL. Nothin but k&n replacement filter. Anyway just set your cruise right after gear shifts and forecast slowing traffic. And try not to prove something everytime the light turns green. Youll be good to go.

 

yea buddy miles per tank does mean something.. i can't figure out my mileage after using only a quarter tank of gas because it takes me 40 miles before i get off of full w/ the needle. and i clearly pointed out that i had the 18 gallon tank. and the reason i used my best is because now i know i could get that again, and wanted to know what i got for that tank. and i did specifiy A tank, not HALF a tank.

 

wait a second, i have 33" tires and 3.73 gears, from what my odometer says, im getting 180 miles a tank roughly 10mpg, what am i really getting?

 

Unless Ford changed something in the last decade it is actually a 19.5 gallon tank.

 

i was getting 21 mpg avg with stock tires on the 3.0, 5 speed ext cab without running ac. . i put the 33's on and my mileage actually became better ..

without using mathmatics so i know there is no flaws. . it would always take me over a 1/4 tank a day to get to work and back .. after the 33's , it takes 1/4 tank exactly to get to work and back .. go figure

 

wow, 4.0 with 19-20 mpgs, thats nice. yeh im hoping my mpgs dont drop too much when i get my bigger tires. ehhh.

 

I have the 3.0 I get 17mpg with 31s

 

Yeah mines and auto though. It could be better with standard but they didnt have one. Keep me posted on your tire info cause Im thinkin of gettin 31s after i get back to Indiana.

 

umm...rand is right here. have ur trip odometer set at zero then drive around...when u stop to fuel up drivide the gallons u put in by the miles driven...and take a running total over 3-5 fill ups...and if u think ur speedo is off add a given percent to the total before dividing ur total gallons u put in.