Hello to all! I am a new user to this site. I have a 02 F-150 Supercab with the 4.2, auto, and 3.31 gears. I just put bigger tires (265/70/16) on the truck and my gas mileage has dropped considerably. My question is Will a new chip, cold air intake, and dual exhaust make the mpg better and is it worth the money? I've been to the troyer performance website and have found several mods I want to do.

 

Welcome new user! Glad to have you here!

Bigger tires with the 3.31 rearend can cause your engine to have to work harder to get everything going. The 3.31 is more of a "highway" gear and putting larger tires on only makes it more so.
Also, larger diameter tires will cause your speedometer/odometer to be a little innacurate. This can make your mpg seem worse also.

As far as your question about the mods, I'd suspect the mods described will improve performance and I'd also suspect you'd likely get in the gas more to enjoy that improvement, and your mpg would likely drop.

To get the full benefit of a chip, you'll have to use premium fuel.

Is it worth the money? Only you can decide that

Just curious, what is your calculated mpg?

 

I figured the mpg to be about 14. If I was to change the 3.31 to a 3.55 or 3.73, would the mpg go up or down?

 

well if it helps you out any i have a 2002 4.2 5sp 4x4 with 3:55 hears 285/75/16's and mine averages out at 16-19 depending on how hevy my foot is!! i also have a K&N air filter might have help might not i dunno

 

I think the gear choice also depends on your driving. For example if you mostly only drive somewhat long distance on the highway, the smaller numbers will help. If your driving around stop-n-go in the city all day then probably a step or two up on the gears would help. My 99 4x4 with a 4.2l and 285/75 r16 tires gets just about what the window sticker said on the truck. The window sticker when I bought it was 15 city / 17 highway and I typicaly average 14-15 city and 16-17 highway (except in the winter it drops nearly 2 mpg on those marks).

BTW, you didnt say if you had your spedometer corrected for the new size tires. That can make a big difference, for example the 285's I put on caused like a 17% difference, meaning about 10mph off at 60mph. That would also make your gas milleage reading go from 15mpg to 12.45mpg if you didnt take the offset into consideration.

Trie size calculators at: http://www.miata.net/garage/tirecalc.html

Also, my larger tires added 80 pounds of weight to the rotating assembly, which I thought was a bit huge... but still didnt seem to make much change on the mpg... maybe like .5mpg at the most.

 

Thanks for the info. I haven't had much time lately to post. My nineteen month old takes up alot of my time. With my last tank of gas I got 17 mpg. I read in another forum somebody had a problem and somebody said to disconect the battery to reset the computer. So I decided to try it with my truck. Don't know if it helped. I also kept my foot out of the pedal. I will keep driving easy for awhile to see if the mpg stays up.