I've had my 03 Screw since Christmas. It’s the 5.4 V8 4X4 with the 3.55 gearing. I bought it from the dealer with 10k miles on it. The MPG has been very disheartening; I have been averaging at best, 10 MPG. When the truck was traded in by the original owner, the dealer put on a set of 28.5x75x16 tires. Would these tires affect the gas MPG that severely? What size are the stock tires for this truck? When I bought the truck, the sales guy told me I would get between 14 to 16 MPG. I have heard that when putting larger tires on then the stock tire, you need to reset the computer and enter in the new tire size. I have no idea if they did this when the put the new tires on. If they didn’t, would this make a huge difference? Anyone have any ideas? I’m dying here since the cheapest price for gas right now in Las Vegas is $2.11 a gallon! Is their anything I can do to get my gas MPG up to where it should? Could the tires be the sole problem? Any help and ideas would be greatly appreciated!
Bryan

 

03 / 4x4 / 5.4 / 3.73 /

12 city
15 highway

Why did they put new tires with 10K miles?

 

larger tires equal slower odometer = your figures would be off

look inside your fuel door for tire size thats where mine is

 

They put the new tires on the truck to make the truck look hot. So do I need to take the truck in and have them reprogram the computer for the larger tires?

 

Sounds like that's what you need to do. Should also being screwing around with your odometer causing you to rack up more miles than you actually are, hence the incorrect MPG. I would be **** and complain to the dealership about this.

 

Actually, taller tires equals slower speedo (truck is moving faster than the speedo says you are) which in turn would mean LESS miles being racked up on your truck. This is what adds to the "appearance" of bad gas mileage. Becaue of the tires you are seeing less miles per tank of gas so when you do the math, the mileage is lower and looks worse to you when in all actuality, you are getting more miles out of a tank than what's showing up on the odometer. Did that make any sense???

 

First, how are you calculating fuel mileage. I mena no offense, but some people really don't know how. Some people take their 24.5gal tank and divide it by how many miles they drive, yet they may only put in 18 gallons at the pump. You may laugh, but I've seen it more often than I should.

Next, look at the driver's door jam and read the OEM tire size. i think it may say the tire size in the fuel door too. 285/75R16 is only about 4% larger than 265/70R17 if that was the OEM size. Play with the math and you'll figure that you are actually getting 4% more miles on that calculation, so 4% better fuel economy. That isn't much, now at 10.4mpg. But, I don't know that 4% is right because I don't know what your OEM tire size was.

Figure that out. Then, make sure the dealer who installed those larger tires either changed the computer or changed the VSS gear.

Also, larger tires are generally heavier which means they have more inertia whcih means it takes more power to turn them. I have abou tthe same size tires and get only slightly more than you, but I also have 3.73 gears and 4wd. I don't know if you have 2wd or 4wd.