josh-emt

When I first bought my truck I got almost 18 mpg. It went down a little over time... Like to 17.3....then I had transmission problems and it went to 16mpg. Transmission is still not fixed in my books although ford says it it. It feels like it slips in 2nd gear at 3k rpm. Either way, I bought new tires the other day. I had 235/75/17. Now I have 285/70/17 on the truck and mile fuel mileage has dropped to 12mpg. What the heck?????

Is this normal? Anyone else have this problem??

snakebit95

I'm averaging about 18.5 with about 60/40 highway/city driving. I also pull an aluminum bass boat twice a week for about 50 miles each trip. I have a regular cab, 2wd, 3.73 gears and stock 20" Bridgestone Dueller tires. I have been really happy with my mileage / use of the truck.

With that said, what is the configuration of your truck? Is your truck 4wd? Did you put an all-terrain tire on the truck? If so, most have a much higher rolling resistance and your mpg's are going to take a significant hit. Have you done any suspension changes to alter the ride height?

Duro

Did you get the ECM flashed to reflect the change in tire size?
If I am not mistaken, the MPG calculation involves the amount of rotations the axle does, therefore bigger tires will give you more miles per rotations.

josh-emt

No i have not had the ECM flashed to reflect the change in tire size.

yes they are all terrain Terra Grappler G2s. I figured i would lose a little bit of mpg but not the 4.3mpg that i have lost

snakebit95

Having your speedometer corrected for the new tire size should help some, but the type of tires play a big role in mileage on these trucks from what I have seen. I can easily get 1-1.5 more mpg's by changing my driving style as well, but I have to constantly focus on it. Instead of breaking all of the time, you can let off the gas pedal early and coast most of the way to stop signs. Learning how to feather the pedal on hills helps too. Unfortunately, I have not been successful at changing my driving habits to maximize mpg's in this way. Lol.

mechanicboy

Bigger, wider, heavier, and/or more aggressive tread will reduce your fuel economy. If your tires are taller then you speedo/odometer is off meaning your MPG calculation will be wrong. If you have a slip in 2nd gear then the aforementioned reasons will make it worse.

tanked_darren

Yes and yes. Bigger, heavier tires eat away at MPG's.

Mattwrotethis

I average 15-17mpg highway driving like I've driven previous trucks that got 18-20mpg or better driven the same way. If I drive like a little old lady and never break 65mph, I can squeak 18mpg out of it.

I didn't buy a truck for fuel economy, I bought a truck because I need one. I bought a 3.7 for fuel economy and because the horror stories from the 5.0 and Ecoboost crowd drove me in that direction.

Other than how thirsty the little bastard is, I have nothing bad to say about the 3.7 in my truck. It sounds surprisingly good (Actually, it sounds downright wicked, especially in the higher end of the RPM band when I'm not trying my best to get 18mpg. I never thought I'd like the sounds a six-cylinder truck made, but the 3.7 sounds good!). It's smooth as hell (more than I can say for the schizophrenic transmission behind it), has more power (not just on paper, butt dyno confirms it) than my last two V8 trucks (4.7 Dodge and 4.8 GMC, though the GMC was hot-rodded later on, stock-for-stock, I'd bet money on the 3.7), and so far (granted, only 8000 miles on the truck) has been totally reliable.

fordguy91

I have nothing bad to say about mine economy wise mixed driving I get about 19 mpg. If I'm on the highway and keep speed at or below 65 mph I get about 21-22 mpg. The best I've gotten was about 25 mpg maintaining a speed of about 55 mph over a distance of roughly 160 miles. My truck is a bone stock xlt 4x4 supercab with 3.73's.

daviesakiller

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