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Old 04-22-2008
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how to calculate MPG

how do i calculate MPG with the new gears and tires?
i have 4.56 gears, 33" tires, and this past tank the trip odometer said 368mi. when i filled up and put 18.6gallons in.

stock gears were 3.55
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Old 04-22-2008
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368 divided by 18.6 = 19.78mpg Now, someone said that 33's knock off about 1 mpg... so ur lookin at about 19mpg. which aint bad, is actually quite good.

but its miles driven, divided by gallons of fuel. its not a 'dead on' way of doing it, but it will get you with in 1mpg of the actuall mileage
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Old 04-22-2008
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^ But what if his odometer and speedometer are off?
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Old 04-22-2008
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And they are off. I know how to do it with different tire size but not different gears.
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Old 04-22-2008
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Easiest way to check your odometer for accuracy is to check it against hwy mile markers.
Check it over a minimum of 10 miles or so. The longer the distance the better.

Let's say you drive 10 miles and the odometer reads 9.5. You are 5% slow.
If it reads 10.5 miles you're 5% fast.

If your odometer says you went 368 miles and it was 5% slow, then the problem would be
368 X 5% = 18.4. 368 + 18.4 = 386.4 ACTUAL MILES DRIVEN. 386.4 / 18.6 = 20.66 mpg.

On the other hand if the speedo is slow then it would be
368 - 18.4 = 349.6 ACTUAL MILES DRIVEN. 349.6 / 18.6 = 18.795 mpg.


Hope that helps

Last edited by MemphisSenior; 04-22-2008 at 12:41 PM.
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Old 04-22-2008
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Old 04-22-2008
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Those don't help with figuring out the different gears
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Old 04-22-2008
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Old 04-22-2008
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The last one is the only thing that could help, but I don't know how to figure it out lol
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Old 04-22-2008
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theres now was hes getting that with 4.56 gears thats way wrong and your speedo is way off you can so and have a new speedo gear installed the right size and all that for around 50 bucks just have to find a place to do it. the reason i know thats wrong is because i have 235 tires and 3.27 gears and my mpg is only 18-19 no way hes getting that
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Old 04-22-2008
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Quote:
Originally Posted by Downey View Post
theres now was hes getting that with 4.56 gears thats way wrong and your speedo is way off you can so and have a new speedo gear installed the right size and all that for around 50 bucks just have to find a place to do it. the reason i know thats wrong is because i have 235 tires and 3.27 gears and my mpg is only 18-19 no way hes getting that
when i was stock, i could get 24mpg highway and 20mpg city... whatever stock tire size was and 3.55s lol.

on another note...

driving next to my friends cars, when my speedo is reading 65, theres is reading 60mph give or take...
so im reading 5mph faster than actual...

i guess i can hook up my dads GPS and reset all the mileage and what not and just drive somewhere over 100miles, and fill up and calculate...

if im getting 18mpg ill be one happy camper for sure!!!
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