drastic MPG improvements and faults

[carfox]

Im pretty sure my 4x4 has 4:11 gears.
it came with the stock 27" 235... something tires.

i put 31"s on it and now the gas millage is down from 22 to 12.... what. the. actual. fvck.....
the truck is totally stock.

what MPGs are you getting? what helped and what hurt?

i may go back to the stock size and just lower/level the rear leafs to it "stands" better.... i hate that pickup truck forward rake angle.

 

[alwaysFlOoReD]

What year truck and motor and transmission? What type of driving do you do mainly city or highway? Did you change how you drive after new tires? The bigger tires will have greater mass and momentum, so will decrease mileage most on a city stop and go drive. As far as rake, its a truck and is supposed to have a rake for when its used as a truck to carry a load. If you want to change it, fine, but don't hate on it.

Sent from my XT1032 using Tapatalk

 

[carfox]

2001 4.0 single cab, auto, 4x4, long bed.

its really 50/50
but yeah... "high flotation" tires, wow....
yeah, suspension compression is a thing, but it still looks and rides lame at that angle.

an electric fan is probably the 2nd best (individual) thing you can do for MPG improvement.

and a 2nd set of tires; apparently....

 

[RonD]

4.0l would be good at 18mpg

Look at door tag to see what ratio you have: http://www.therangerstation.com/tech_library/axle_codes.shtml

Tires size changes from stock size(on door tag) means speedometer will be off, so Odometer will be off as well, and if you use odometer to calculate MPG then...........it will be off.

 

[kunar]

did you calibrate your speedometer after you changed tire sizes?

 

[cp2295]

Yeah it will be off by a percentage. My rig has 31s and stock size is 235/75/15s so right now it's about 12% off. So u must factor that into your calculations. I just multiply the miles on my tripometer by 1.12 to get the correct mileage.


Sent from my iPhone using Tapatalk

 

[ridgerunner]

Mine did that last yr about this same time of year. I switched from 29" tires to 31's. Winter blended gasoline will give U crappy MPG. Wait till spring/summer and it will change back some. U should loose about 1-2 mpg with the larger tires. I went from 18-21 mpg to 15 with the tire change, then changed back to 29" tires and mpg was nearly the same. Winter gasoline my friend!

 

[hondaxr650]

If you didn't correct your speedo for the tire change, your mileage readings aren't even close. From a 27 in. to a 31 in. tire there is a huge difference in the revolutions per mile. I went from a stock 31ish in. tire to a 33x12.50, corrected the speedo and it made no difference in gas mileage whatsoever.

 

[Grey_04]

Don't for get you don't get decent gas mileage out of the winter blends of gas you get from summer.

Are you idling a lot or doing more city driving? these all add up to poor gad mileage.

 

[carfox]

4.0l would be good at 18mpg

Look at door tag to see what ratio you have: http://www.therangerstation.com/tech_library/axle_codes.shtml

Tires size changes from stock size(on door tag) means speedometer will be off, so Odometer will be off as well, and if you use odometer to calculate MPG then...........it will be off.

THAT was helpful, thank you.
i have "96" so open diff, 3.73.... 31s should be prefect.

 

[RonD]

THAT was helpful, thank you.
i have "96" so open diff, 3.73.... 31s should be prefect.

If original tire size was 27" and new tire size is 31"
Then 3.73 ratio would "act like" a 3.25 ratio after the tire change.

If speedometer was showing 40mph actual speed would be 45mph
If speedometer was showing 60mph actual speed would be 68mph
If speedometer was showing 70mph actual speed would be 80mph


This lower ratio also makes for less low end power, but lower RPMs at highway speeds, so better MPG, but that is usually negated by the heavier tires and taller stance.

Also odometer showing you traveled 70miles would actually mean you had gone 80miles
100miles on odo would = 114.7 actual miles traveled

So multiply odometer miles by 1.147 to get actual miles traveled, and then use that to do MPG calculation

If odo showed 200miles then 200 x 1.147 = 229.4 miles actually driven
229.4 miles / 13gallons of gas used = 17.64MPG

 

[ridgerunner]

FYI I am now getting 15mpg with winter gas here in N.Central PA. Just a few weeks ago I was getting 18mpg. The winter gas switch is on!