On the end of my recent run after filling up my tank, I did a manual calculation to compare results from the fuel computer on the F150. The manual calculations agreed with the fuel computer, both identical 20.9 L per 100km. (approx. 11.3 mpg US). That was after 392.6 km on 82.2 L of regular gas. This included pulling a 21 foot trailer about 5500 lbs for approx. 200 km. My previous calculation showed a difference of only 0.2 manual versus fuel computer so it seems that the fuel computer is fairly accurate.

Just saying.

 

Looking for an answer to likely a stupid question......I dont fully understand all the discussion on different rear ratios etc to improve gas milage but was wondering, since gas milage appears to drop at higher speeds, what affect would taller tires have on gas milage? That is if the sweet spot for a particular set up was 60 mph and you typically drive 65 mph, if you put on taller tires, would that mean that you would be moving your sweet spot for gas milage higher, or does that simply give you a false reading on the speedometer? I know stupid question but nevertheless I have wondered about this lol. Dennis

 

Taller and heavier tires decrease fuel economy. Anytime You increase your rolling resistance you will see a decrease in MPG.

Your dealer can reprogram your computer to compensate for the different size tires and make everything accurate again.

 

well my last in town tank was 14.82. Not too shabby really. My problem is I can't hardly stand to keep my speed under 70, and now with the speed limit going up to 80mph across Wyoming I'll never get the advertised mileage. haha

 

The nice thing about long drives, even if it means taking some side roads to avoid KC rush hour traffic.

 

Just completed a trip from Ga. to Wisconsin and back. The lowest mpg was 19 and the highest was 20.5. Tried to keep it at 75. 5.0 with 3.55 rear end.

 

Just finished a trip from Lawrence KS. to Santa Fe New Mexico. Pulling a loaded u-haul trailer into a 40 to 50 mph headwind and never making it into 6th gear I averaged about 11.6 on the way down, speed at 60mph. Return trip with no trailer and not so much wind,r.p.m.s at 2000, (which is 72mph.) Averaged 20.6. 2009 straight cab, long bed xlt 4x4 5.4 liter, 3:55 axles.

 

Is 3:55 standard or an option gear ratio?

 

I read just a few pages hear and read where mileage gets better after time..
can't wait! 2014 FX4 / 5.0 / 3.55 first tank full was 16.5 - thats partly the salesman let it run for about an hour in the lot before i drove it off.
So far the 2nd tank full is showing 19 on the trip meter ...better than the wrangler I traded in

 

Put in a Poweraid throttle body spacer and its helped my MPG. Went from 13ish in city to 15.7. For highway went from 14.8 to 19.7. I haven't done any calculations yet but I have a few long trips this summer where I can do the math better on it.