So I am planning some trips this summer, and my fuel gauge is not the most accurate thing in the world. if you accelerate/turn right you can lose as much as half a tank of gas, only to get it back when you stop/turn left again.

I have an 89 with a 4.0 2" lift and 31" tires and a 20 gal. tank (according to my build sheet) I filled up when it showed about 1/4 left in the tank and got about 12 gallons into it.

I need to figure out how much my odometer is affected by my tires, and then figure out how many miles I can go on a single tank to plan my trips. My other car, also has a 20 gal tank but gets more than double the fuel economy so I'm used to driving 6-700 miles without having to get gas on a long trip, so this is new territory for me (planning on where to fill up)


so people with stock to slightly modified cherokees, how many miles do you average per tank?

 

Ill make it simple for you. No other persons jeep and driving style matches yours. If all highway, you can get as much as 350. Best thing to tell you is fill your tank. Drive a tank on the highway alone. Fill back up and divide number of miles driven by how much you put in. Repeat process for all city and then mixed city and highway. Done deal. You have YOUR JEEPS mpgs

 

I see close to 300, or just above 300 miles on each tank. My daily drive does not put me on the freeway at all.

 

Thanks JPZ, My last tank got me about 170 before I filled up at a 1/4 tank, (trying to account for the larger tires). which seems super low, but I do drive in heavy rush hour traffic on my way home with the A/C running. I calculated to about 13mpg, which seems very low to me.

 

http://www.tacomaworld.com/forum/tirecalc.php

you can use that to determine which percentage your ODO/speedo is off by

if stock tires were 235/75/15, 31s would be 6.8% off.
if stock tires were 215/75/15, 31s would be 10.6% off.

 

Bone stock 99 automatic I get about 275 miles per tank mostly city driving.

 

Perfect, thanks!

then yes, my last tank of gas brought me 13mpg... not great... but it was my first tank of gas that wasn't driven with it very broken, so hard to judge off just one tank. Will need a couple of fill ups to figure that out.

My bigger tires should give me a better MPG on the highway if I keep my speed in check. but I've been driving 65 mph per my speedo which is 72. if I keep it closer to 60 mph per my speedo, I should be within the speed limit and get better highway mileage.

Big problem is my drive home, a lot of stop and go and crawling along at between 5 and 15mph.

last tank was 170ish miles (got the new tires half way through that #) we'll see where this tank gets me.

 

bigger tires will make it so the engine revs lower at hwy speeds, BUT you need to also consider unsprung weight increase and higher rolling resistance with A/Ts vs street tires. Additionally, the extra height added (a couple inches) is only going to hurt you aerodynamically. Not trying to be a downer! I have a 2000 4.0 4x4 auto with 31s and 3" lift and get about 320 mi to a tank if I drive conservatively. aka, 16mpg. lol damn that actually makes me kind of sad.

 

if I can get 300 miles to he tank, I would love it. I drive conservatively, I'm no speed demon in my jeep, but this won't get driven all that much. its going to be the car my wife drives (stay at home mom) when she needs to take a kid to the dr.s, and for us to go camping with. I have another vehicle that is my commuter (saab 9-5 aero with a stage 2 tune....)

However, 170 miles to the tank/13mpg is a bit painful...

 

170 miles / 20 gallons = 8.5mpg. you sure youre only getting 170 miles? is that before multiplying by 1.106 to account for odo accuracy? even still... dont know how you get 13.

when did you change your plugs last? the coppers are only really good for 30k. after that, MPGs can really suffer.

 

I never run to empty, I fill up when it shows about 1/4 tank. I put 12.77 gallons in, had 160 miles on the Tip, The last 60 or so were driven with new tires, so if the Trip was accurate for the first 100 + 66 (60x10% difference in tire revolutions) so 166ish miles/ 12.77 gallons at fill up = 12.99 mpg.


Plugs are almost brand new (less than 2k miles) I've only owned the jeep about 2 months, and the first two months were fixing issues. like all new vacuum lines, new cat, new plugs, new gaskets everywhere, etc. Its only been really driveable the last two weeks. so I'm just trying to get a judge for where I am at. I don't want to plan a trip with a 250 mile stretch between gas stations, and not be able to make it. Planning on visiting my brother in tx end of the summer/fall, from AZ, and it is possible to go that far between fill ups.

 

I get about 220 a tank, 3'' and 31s. Spirited driving lol

 

do you fill up at empty? that's only 11mpg...

 

Do you know if the o2 sensor have ever been changed out? A fouled o2 sensor can give you lower mileage. Just a suggestion.

 

Thanks, I do not know if it has been changed or not recently it has not been changed since I've owned it. So def. the next place to look if my economy doesn't increase in the next couple of days.