hmmm..just a thought

[noskils32]

Hello all, I was thinking today why I get such poor gas mileage with an inline 4 (12mpg). I kept telling myself, "It's the 33s and the lift...It's my poor driving habits"...but I was thinking today. Is it really? Ever since my bigger tires, my speedometer doesn't work right. Could my mileage counter possibly also not be exact thanks to the bigger tirees? It this possible? I tried to prove it by using the exit signs on the freeway but it was just too hard. Am I getting better mileage than I think?

 

[MerkL]

If you speedo is off, then your mileage counter will be off too. I had those exact same thoughts when I got my lift on.

 

[avyoung]

Yes. You can do a calculation to figure out how far off you are then recalculate your mileage. If I can find my book I will post the calculations.

You can also replace the gear to recalculate. It is around $20 and looks pretty easy to change.

 

[Snitty]

you are really traveling further than your odometer says you are

 

[Bounty__Hunter]

Find the percentage difference between the stock tire height and the new tire height. Going from a 27" tire to a 33" tire is about a 22% increase. Multiply your odometer by 22% and add that result to what the odometer reads, and you can figure your new mileage from there.

I went from a 41tooth speedo gear to a 35tooth speedo gear and it corrected my speedometer and odometer. It's on a 2.5L YJ with 4.11 axle gears, going from 27 inch tires to 32" or 33".

Check out XJ's at the junkyard, most 4.0L autos have 3.55 axle gears and the 35tooth speedo gear, be a good donor. Get the speed sensor with the gear, they can go bad.