I have 285/16's BFG's on my 01 SC 4x4 with the 5.4 automatic and 3.55's. My mileage has been getting pretty bad, and I'm wondering if anybody with the same set up has some numbers for their truck. It got worse when I went to setup and I knew it would, but the price of gas has made it pretty painful. The truck has about 70,000 miles on it.
Thank,
slarson

 

I average 13-13.5mpg on my 2wd lowered 3.55 4.6 03 with 36k

 

Make sure you are adjusting for the bigger tires when calculating your mileage. I have the stock 255/70/16 tires and I'm getting about 16mpg average right now. My mileage was also starting to suffer and then I had a coil fail - changed coils and plugs and my mileage came back. I have 65K on mine.

 

I assume you have 285/75R16 tires, very similar to 285/70R17 that I and many others have.

I put these tires on before I filled up the first tank, with only 200 miles on the truck. The tires are 3.5% larger than my stock size of 265/70R17. 2003 Supercrew 5.4L 3.73LS.

I have always gotten 11-12mpg with it. Sometimes 13mpg on the highway, but usually 11-12 in both city and interstates. I've gotten two tanks just over 14mpg in 38k miles.

I had a 99 Supercab with the exact same drivetrain. That truck would get about 2mpg better than this truck under the same driving conditions and style, even if I had an extra 300 pounds in the bed. I believe the biggest factor is the extra 12 pounds for each tire. That's a lot more mass to rotate.

 

Thanks for the replies. I do have the 285/75/16 BFG AT's on it. I get about 12 around town and 14-15 on the road. My speedo seems to be saying the correct mph according to my GPS, but who knows. How would I account for the differerence in the tires? Is there a formula?
slarson

 

Tire sizes are rough estimates of physical tire size. Check outTirerack's Tech Cener first. Then, see Miata.net's tire size calculator to do the math for you.

 

Keep in mind since you installed a taller tire your speedometer/odometer is off. So, you are actually getting better MPG's than your figures show unless you correct the speedometer/odometer. What size were your OEM tires?

 

I average about 14.5- 16.0 mpg city/highway combined. (mostly h/way)
Tires are 265/70/16's (stock size was 255/70/16) 4x4, 4.6L w/3.55 l/slip.

Mike

 

I have a 5.4 4wd w/ 315/75/16's on it also with a 3" body lift and my mpg is around 11. When you go to a bigger tire you will lose some mpg unless you regear it to compensate for the change. My truck still has the 355 gears but those will be changed soon. I also have a locker setup thats going in there also.

 

Wandell,
I can't remember, but I think they were 265/17's.

 

Just sold my 01' screw 4x4 5.4 had the stock 255/70/16. 96,000 miles on it and I was getting a solid 16mpg around town. I had a light weight canvas Tonneau cover made by "Lorado Roll-Up Cover". I think that Tonneau cover helped the miles per gallon out alot.

 

5.4L rocking Goodyear Wrangler AT/s 265/65/R17s & I average 15mpg city, highway unknown