Another poor fuel mileage problem

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Dec 31, 2005 | 01:09 PM

#21

bob200587

Contributing Member

Joined: Feb 2005

Posts: 3,546

Likes: 1

From: Nashville, TN

Quote:

Originally Posted by hill

17.8% difference.....dam.... i only figured going from 31" to 32" on my truck worked out to about 4%....did i do my calculation wrong or something???

Does the VAF actually affect mileage??

I would have thought replacing the O2 sensor would have got it.

if you're truck came with the stock 31s then it would be only 4%, but with the 225s it would be alot more. It took me a while to figure it out because I'm not too good with algebra, but its really just a simple equation

(Original tire diameter in Inches) * X(%) = (Difference of New and Old Diameter in Inches)

Solve for X and you have the percentage that the odometer is off. Correct me if I'm wrong, but it should tell you how much the speedo is off as well.

Jan 1, 2006 | 08:33 PM

#22

hondacrusher

Registered User

Joined: Dec 2005

Posts: 20

Likes: 0

From: Colorado

there are a bunch of charts around the internet that tell you what speedo gear is needed for the tires you have on now vs stock tires. ive found it easiest just to change the speedo gear for a mechanically driven speedometer. during winter they change the fuel mixture which results in about 75 mi less per tank than summer for me. i cant remember if its ethonal to methonal or vice verso