guys if you can help me out, i recently put on new tires on my 99 F-150. i dropped rim size from a 17" to a 16" and rasied the size of my tire from a 265/70R17 to a 285/75R16. There is roughy a 1" difference but it dropped my gas milage from 16 to around 11 or 12. Now how di i correct it and possibly increase my gas milage? i am open to any and all upgrades.

 

I dont think the overall size is the issue. The extra weight of the tires is probably the deal. What type wheels and tires did you go to? The smaller rim negates some to the larger size of the tire. Are the wheels the same weight of what you took off?

 

The tire size is around the same high, just an inch difference. The rims are aluminium and as for weight, they don't feel any different then the stock chrome steal rims and tires i removed. the RPMs are roughly the same driving down the road, it takes a little more on the take off. if by adding a new exhaust and air intake will that get my HP and torque up enough, or should i change up my gearing?

 

How are you computing your mpg? Are you just taking what the odometer says and dividing that into the gallons of gas used?

Did you re-calibrate your odometer for the increased tire size? If not, then that's where you have "lost" your mpg's....

I did the same thing when I went from the stock 255/70/16 to 265/75/16. I was computing directly off of what the odo was saying. Once I figured in the % that it was off, I was back to normal. I then got the odometer re-calibrated which also fixed the speedo (because it's off too). I was able to just swap out the VSS gear, but you will have to do it with the computer and a programmer.

Good luck!

Mitch

 

A little is off due to the 1" larger diameter (3%), but 3% does not go from 12-16mpg. The penalty is the hevier wheel/tire combo. You said yourself that it takes more pedal to get up to speed. Well, that's the extra gas. How will you get back that fuel economy? Drive slower or go to ligher wheel/tires. No amount of aftermarket items will gain 4mpg.

 

Another thing that will affect your mileage is the type of tire and / or inflation pressure. Some tires have more friction / drag than others. For instance, an all out mud or rock crawling tire will have miserable mileage when compared with a straight summer tire - all other things being equal.

 

Oh yeah, like said above check the air pressure. If they are light truck tires then they prpbably require a lot more air pressure. Mine can hold up to 50 psi but I have 40 in them. They were originally aired up to 35 psi and felt mushy.