p38fln

SIX MPG towing an 8,000 pound trailer? How steep are those hills?!

We've got semi trucks pulling 47,000 pound trailers that get better fuel efficiency than that! And they also have 3.73 rear ends.

Also be aware that as winter sets in your fuel efficiency will go down due to more dense air (I've heard up to 10%), and since you're in Canada, you won't get the extra bonus of more BTU's per gallon of gasoline when it contracts at cooler temperatures, because Canada uses temperature compensating fuel pumps.

For some reason, temperature compensating fuel pumps aren't economically viable in the USA where the average fuel temperature is over 60 F...(The 'trade' temperature)

bubbabud

Its not the denser air its the winter blend fuel which is more vollittle and a lower flash point . As for the semi with much larger tires 3.73 is relitivly high gearing many run 4.44 gears. Diesel also has a higher energy content than gasoline Bubbabud

TJPlatinumEB

I'm going to have to disagree with you there, at least in my case with my truck. I drive A LOT of highway miles and in all different sorts of terrain all across TX. I've got almost 8k miles on my FX2 w/ 3.55's and can easily make 21.6-21.9 at 74mph with the cruise on going all over the various Interstates that I travel on. I have had two full tanks of gas where they were literally 100% highway miles without stopping once and got 21.7 and 21.9 respectively with an average mph of 73-74 giver or take a few slow people in the fast lane. Went over 540 miles on each tank. Those are just the two examples where tanks were 100% highway, but they aren't an anomoly. I consistently get over 21 up to 75mph. After that it of course drops off significantly. These are also hand calculated numbers, not using the truck's calculator.

I've made numerous posts on this forum about this and it is not just doing 55 on a flat road. I have no reason to build up or one up the next guy. If I wasn't happy or had issues, I'd be first to say so and hopefully keep someone from doing something similar. I do agree that it seems to be very weird that some have horrible luck and others have great experiences with the mileage.

My window sticker advertised 16city and 22hwy. I get VERY close to 22hwy and get right at 17 with mostly stop and go city driving.

To the thread starter, I would definitely have it looked at and not let them give you the break in miles excuse. It's obvious you have done more than that and have multiple instances of bad mileage. Sorry for your bad luck but hopefully you can get it worked out.

69428SCJ

17 mpg on the highway with 34's really isn't too bad. Not sure why it's not picking anything up when the stock tires are put back on. Check your tire pressure routinely. The on board monitor will not light up until the tires are around 25psi. If you had a 5.4 that got 23 MPG you need to go find it and let Ford replicate it about 1 million times a year.

I'm driving your truck with the same gears and a 6.5 foot bed and routinely see 20 mpg at 70-72 mph here in terrain friendly Texas. I just got back from driving it 2600miles in 3 days going to Las Vegas and back to pick up an old motorcycle. The cruise was set at 80 mph the entire time...the speed limit in West Texas. 75mph is the limit everywhere else I drove. I averaged 17.2 over the trip. I had bad headwinds and 700lbs in the bed coming back. Best was 18.8 and the worse was 15.9...YUK!

Kenneth Forbus

Like said above the gears is a lot of the issue. Running the 3.55 or less gear would have gained some MPG. My "real" numbers with Ecoboost XLT SCrew 3.55 is 18.5 on a average tank. I can pull off 21 out of a tank but it is a pain in the rear between using cruise control, coasting down grades and using the least amount of petal to make it up hills. This mileage is all rural country two lane roads around 50 mpg with a few stops here and there. My only highway trip got around 20 mpg @ the posted 70 mph.

Most of the mpg issues I have read about have been 3.73 geared trucks. Some people have got decent mileage out of them but I think that is your root cause for your mileage.

A close friend of mine bought a FX4 with 3.73 three months ago and just traded it in on a more fuel efficient car due to bad MPG. We even swapped trucks for a day to see if it was the truck or foot. In the end we could not get better than 16 when my truck on the same route would get 18 or better. Either way I wish you the best of luck.

69428SCJ

I'm with you 100%....but for some reason the Texas driven trucks seem to be doing really well. Not sure if its our mild temps and flat highways or what. I drive to San Antonio almost every week from DFW. If the winds blowing I am at 19 going down and 21-22 coming back.... or vice versa. The tank always averages a little over 20 mpg when I fill back up in Waco coming back. Cruise is set at 70-71 mph.

69428SCJ

All things being equal a 3.55 gear change to 3.73 is not worth 2 mpg. It is simply not a big enough change...less than 5%. If you take the same truck and swap the gears out of it instead of comparing two separate vehicles you would not see a 2mpg change.

jesusers

I've gotten 15.1 over my first 1700. Lots of idling to show it off and a few "over accelerations." Each tank has been better, but it's hard to say if I'm driving differently or if the "break in" period is nearing the end. Mostly city driving, my daily highway commute is 4 miles, the rest is all stop and go. On a 100 mile trip i got about 22 into the wind halfway.

deLfiZziXx

I havee a 3.55 and have had two motorcycles in the bed and tons of equipment in the cab. Averaged 18 mpg going up and down hill....

On a trip to vegas with 4 passengers I averaged 21 MPG

oxfordboostd

im in tulsa ok and see very similiar numbers and i wonder if we have a better fuel quality?