facts about gear ratio and mpg

[craveman85]

i read an article online that the difference between gear ratios and mpg isnt that much. http://www.trucktestdigest.com/axle ratios.htm they say the difference is in fractions of 1mpg. so i decided to do some testing. me and my friend both have 2004 ford ranger edge 2wd's with 3.slows and 5 speeds. he changed his rear axle out to 3.42 because he spends a lot of time on the highway. i have 4.10's in mine. we also have the same tires because we both like the kuhmos we have. for 1 week we each drove our own trucks at a steady pace to work. then we switched trucks. after some careful calculating we found that my truck only got .5mpg less than his truck. his truck averaged 21 and mine averaged 20.5 so for 15k miles in a year he would spend 2714 in gas at 3.80 a gallon. i would spend 2780 in gas. to me that extra 66 bucks is well worth the extra gearing. so now that you see its not going to cost you that much go out and swap your rears!

 

[dla]

Good info. Thanks.

 

[scotts90ranger]

on my truck I went from 4.10's and 31" tires getting a steady 15-17mpg. I recently lifted my truck to fit 35's and put 5.13's in it. The past two years I've made a trip to the center of the state that involved going up a mountain pass, last year with the 31's I got 15mpg up the pass, this year with the 35's I got 18mpg and yes I corrected for the inaccurate speedo...

 

[4x4junkie]

I always tell people, go for the gear. RBV engines (especially those smaller than the 4.0L) are completely happy spinning along at 2500-2700 RPMs on the highway without a loss in MPG

If I was gonna guess, Craveman you're running stockish size tires on your trucks (215/70R15?), your MPG would probably be right at peak if you had a 3.73 axle.

 

[craveman85]

235/70 16. may go narrower if i can find one tall enough. im a big fan of skinny tires like the old jeep tires.

 

[4.0B2]

which is why i'm gonna do 4.88's i'm sure!