Tires 1" larger than stock-is it affecting the pcm

[denali_dave]

i am getting terrible gas mileage. when i ck the speedo compared to like a mobile radar speed indicator, its right on or so it seems.  besides a power programmer, is there a cheap way to recalibrate the computer?  I wondering if this is why the mileage seems so low?

[wonderl33t]

I am  curious also.  I swapped my stock 16" rims for the 17" Denali XL rims and I also noticed a drop in gas mileage.

 

I believe there are two factors affecting the mileage:  1)  the tires are bigger meaning you go farther with each revolution and 2) increased ride height means increased aerodynamic drag which results in slightly worse mileage.  So I would guess that you and I get roughly the same mileage as before.  

 

I know the Hypertech programmer can recalibrate your system, but it costs $300.  I am wanting to get it for the power increase anyhow, though.

[denali_dave]

I havent heard such good things about the Hypertec device as it is mainly for wide open throttle.  I just ordered a Superchips device and will see how that does since it affects part open throttle as well. It also allows you to calibrate for tire size.  I just put on a magnaflow cat back exhaust and it seems to have helped the power some; dont know about the mileage and probably wont until I take my foot out of it for awhile    It sounds pretty sweet!  After this tuning update, I will wait to see if I need to add anything else.