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Discussion Starter · #1 ·
Lately I have seen many posts about lousy milage...seems like a new one every day. I wanted to say that the search feature will give many results on poor milage, AND...
1. winter gas mix is different than summer, and your milage will drop
2. warming up your truck in the AM is burning fuel without gaining miles, your milage will drop
3. putting bigger tires on will cause your odometer to read less than actual miles causing your milage calculations to be off. get a GPS(buy or borrow) drive 100 miles according to the odo, then check the GPS for ACTUAL miles driven. then you can figure a % variance and calculate mileage better and be aware of the odometer variance to know the actual miles on your truck etc..etc..etc.. You might be surprised to find out how wrong your ##'s are esp with 33's or bigger!!!
4. Putting sliders, bumpers, toolboxes, tow straps, OBA, Hi-lift jacks, and al the tons of gear and Misc. shit we carry with us adds weight..and it adds up quick, this reduces milage too!!


Now add up all the factors (1-4) I have listed and any you can think of, re calculate your milage based on the GPS info, and in my case it turned out tha I was actually not getting tha bad of milage ( about 16-18mpg) with a heavy right foot( I dont like to be the last on to pull away from the red light!!!)

Hope this helps with the never ending milage questions.

PS: I noticed that in the "defend your purchase" thread no-one mentioned milage as a reason for buying Tacomas anyway!!! :)
 

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You don't need to get a gps or drive 100 miles. Just a little math should suffice. Assuming stock to be 31" (or 30.6" to be exact). 32" tires would be roughly 3.4% larger in circumference and 33" tires would be about 7.25% larger. Multiply your odometer reading by 1.034 or 1.0725 and divide by gallons added and - tadaaa - corrected mpg.

265/70R16 = 265/25.4*0.7*2 + 16 = 30.61" tall (31")
265/75R16 = 265/25.4*0.75*2 + 16 = 31.65" tall (32") so 31.65/30.61 = 1.034
285/75R16 = 285/25.4*0.75*2 + 16 = 32.83" tall (33") so 32.83/30.61 = 1.0725
 

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AND:

5. Increasing your tire size will also increase your rotational mass and frictional coefficient which decrease your fuel economy.
6. Raising your truck will result in decreased aerodynamics which decrease your fuel economy.
 

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Discussion Starter · #4 ·
I was never great at math so I chose the not so scientific method , but thanks for the formulas...it works out very close to the ##s I got. great points for 5,6!
 

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dougtrd said:
3. putting bigger tires on will cause your odometer to read less than actual miles causing your milage calculations to be off. get a GPS(buy or borrow) drive 100 miles according to the odo, then check the GPS for ACTUAL miles driven. then you can figure a % variance and calculate mileage better and be aware of the odometer variance to know the actual miles on your truck etc..etc..etc.. You might be surprised to find out how wrong your ##'s are esp with 33's or bigger!!!
I went from factory 31's to Dunlop 35's (34" measured). I sit in traffic a lot so I have had ample opportunity to measure actual vs. odometer mileage. I found that my odometer is off by .5mi every 10 miles. Now if I take that measurement and figure it against a 60mph drive, i would actually travel 57 miles, making my speedo off by -3 mph, which I have also found to be the case. The question remains: why isn't my odo/speedo as far off as some I have seen? The only thing I can think of is that I have ABS and the odo/speedo may be taking a measurement at the tone ring(on the spindle/bms) and making a calculation based upon that input. Anyone else running ABS and larger tires find this to be the case?

Boheefus
 

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Tufemup said:
You don't need to get a gps or drive 100 miles. Just a little math should suffice. Assuming stock to be 31" (or 30.6" to be exact). 32" tires would be roughly 3.4% larger in circumference and 33" tires would be about 7.25% larger. Multiply your odometer reading by 1.034 or 1.0725 and divide by gallons added and - tadaaa - corrected mpg.

265/70R16 = 265/25.4*0.7*2 + 16 = 30.61" tall (31")
265/75R16 = 265/25.4*0.75*2 + 16 = 31.65" tall (32") so 31.65/30.61 = 1.034
285/75R16 = 285/25.4*0.75*2 + 16 = 32.83" tall (33") so 32.83/30.61 = 1.0725
Hey-
I have found that according to my GPS, my trucks speedometor/odometer are more accurate w/ 32's than w/ the stock 31's. So you shouldn't add 3.4%, instead, you should do nothing cuz 32's are more accurate than 31's, but it's not our fault the speedos are off from the factory making us think we get better stock milage than we really get.
-Chris
 

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The Satanic Panic
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or regear so that u dont get a speeding ticket like i did :banghead: OD clocked at 60 mph but in reality i was going 64,65, luckily i had not pts taken off :D
 

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always a Toyota lover at heart
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off the subject:
what does your avatar mean? is it the Polish crest?
 

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The Satanic Panic
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raymond watts, industrial artist
 

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PismoBoy24 said:
Hey-
I have found that according to my GPS, my trucks speedometor/odometer are more accurate w/ 32's than w/ the stock 31's. So you shouldn't add 3.4%, instead, you should do nothing cuz 32's are more accurate than 31's, but it's not our fault the speedos are off from the factory making us think we get better stock milage than we really get.
-Chris

I just got 32's put on the other day and noticed that the speedo was almost direct on at like 75.
 

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I had 30s and now i have 33s i divided 33/30 and got 1.1 multiply that by the odometer and divided by gallons... that gave me 18.7 mpg am i doing this correctly..
 

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KillChain said:
He's a Strum and Ruger Gun fan...........
its the company logo.
It's Sturm, Ruger and Co. ;)
 
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