Mpg Drop!!

[NCjeeper]

my jeep has the digital readout of my miles per gallon, and i dont ever really check it because since i got it ive got about 20-22 mpg. when i put on my 31's it dropped to about 20. i put on some 32's a while back, and i checked for the first time since before i put the new tires on, and its a clean 15MPG there has to be something more to it than that? how can a 1" larger tire make me drop an overall of 5mpg?


what do you think fellas? sensor?

 

[jay79cj7]

Did you adjust your speedo for the new size tire? If not, that's part of it.

 

[sicnik]

somewhere here there is a thread with a formula to figure out your your actual MPH/MPG when changing tire size. If I find it I will let you know. You will be surprised at how much you loose when changing tires. Another way to figure out your actual MPG is to start at a mile marker on the highway, set your trip to 0000 and drive to the next mile marker. Then divide what the trip meter says by the miles driven and then add your answer to the miles driven. then take that # and divide it by Gallons of gas used. you should get the correct MPG. Or I could be way off here......didnt do well in math.

 

[NCjeeper]

i dont really know how to? that makes perfect sense though

 

[sicnik]

I found it look in search for " MPG & Odometer withe bigger tires", posted by BostonJeep on June of 03.
Nick

 

[CherokeeGuy42]

20-22mpg? How are you pulling that out? I can barely get 18. What is the stock size tire for an 01 XJ anyway? That could be one problem, I'm running 235's I believe. I'm about to get new tires and I think I'll just go for stock so I can get better gas mileage. $60+ a week for gas is killing me.

 

[90growler]

20-22mpg? How are you pulling that out? I can barely get 18. What is the stock size tire for an 01 XJ anyway? That could be one problem, I'm running 235's I believe. I'm about to get new tires and I think I'll just go for stock so I can get better gas mileage. $60+ a week for gas is killing me.

225/75/15 is the stock size (almost positive)

 

[graewulf]

My 95 ZJ gets about 21-22 with 30's on it.

 

[NCjeeper]

20-22mpg? How are you pulling that out? I can barely get 18. What is the stock size tire for an 01 XJ anyway? That could be one problem, I'm running 235's I believe. I'm about to get new tires and I think I'll just go for stock so I can get better gas mileage. $60+ a week for gas is killing me.

coast when you know a light's going to turn red. dont hold your foot on the gas when going down hills, take off a little slower....etc. i used to get about 18 avg until i starting trying to be more conscious about my driving/gas. i was suprised how many times i'd keep my foot at the same spot when going down a hill. small things make a difference.

 

[CherokeeGuy42]

I put my jeep in neutral when there's a decent hill, stop lights, traffic, etc. And I try to lay off the throttle, but that doesn't work as well. The only time I notice a change in my mpg is when I'm doing highways for a while. Any mods I can do to my jeep to help out?

 

[jay79cj7]

The true distance traveled when you go up in tire size is directly proportional to the ratio between the new and the old tire diameter/radius/circumference (all the same ratio). All an odometer does is count how many times that tire turns and a tire has a set circumference. You just have to adjust for that extra distance around the tire. For instance if you went from 30's to 33's, you would multiply what your odometer reads by 33/30, or you could just add 10%, its all the same.

 

[graewulf]

if you want the best mileage that you can get.. use the cruise control whenever possible.. it really helps. I just got back form an 800 mile trip with the ZJ and according to the computer, I got just over 21 MPG - and that was going across PA into WV through the mountains. I get nearly 500 miles on a tank.

 

[CherokeeGuy42]

800 mile per tank? Geez I'm lucky to get 300 now a days. I used to get around 350, but now I'm squeezing 280 on a good day. Oh and I don't have cruise control. I'm going to use this tank to experiment with easy driving and then at the end of the tank I'm going to do oil change, spark plugs, air filter, work on my brakes, fuel injector cleaner, hopefully get new tires, and try the light driving agian and see what kind of improvement I get. Any other ideas to do when I do all those changes?