Jeep 2k wrangler bad fuel economy
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Gerald and Snark

Anchorage, AK

#41 Aug 20, 2009
I bought a NEW 2003 Wrangler Sport off the showroom floor and put on 31x10.5R15 BFG All-Terrains after only 900 miles on the odometer as it came with 3.73 gearing. It's also a 5-speed with cruise control with a hardtop and the bulletproof AMC 4.0L inline six. I got 20MPG with the cruise control as I kept the thing under 60MPH. I changed over to Cooper STT tires and it dropped by 2-3MPG and I do more city driving. Even with the free flowing exhaust pipe and intake, it's about the same. A dirty fuel system and dirty throttle body will cause bad mileage along with quick acceleration and excessive hill climbing if you live near a mountain top. Use quality top tier gas as well like Chevron as that'll help.

Marquez, TX

#42 Jan 4, 2010
I ahve a 2000 jeep wrangler wit 3 inch lift and 124,000 miles and 31x10.50 tires. everything is basically stock even the air filter and I was getting 20mpg untill recently. now I am getting 12mpg. I am sure my catalytic converter is getting stopped up so I am just gonna gut it. The problem with the 4.0 is that the powerband is too high. So turbocharge it and set your wastegate at 6psi with full boost at 1200rpms along with a custom ground cam. A good turbo can often be found in a junkyard but if you are inexperienced then see a performance shop. 6psi will keep it reliable but scavenge all the exhaust gases out of the cylinder with the new cam at a low rpm. Also it will add about 80hp and 100-120lb/ft of torque at this lower rpm while not requiring much more fuel, and it is cheaper than swapping in a dang chevy motor that wont last as long.

Chapin, SC

#43 Apr 7, 2010
pete wrote:
Hello ALL,
We just purchased our 2000 jeep wrangler 4.0 automatic with 64,000 miles, I had it checked out by jeep dealer & they said the jeep was in excellent condition.
My current problem is that I am only getting about 10MPG fuel economy. I was wondering if anyone had similar issue & what was the fix.
Couple of friends suggested that their 91 jeep had bad catayltic converter.
I have a 02 sahara 4.0 auto with K&N air filter, Bosch Plat plugs, Banks high flow headers w/banks monster exhaust, plus flow master high flow cats. On pennsylvania highways @65 mph I get 18-20 with great power band increase.

United States

#44 Oct 27, 2010
TIM wrote:
Should the 4.0 be abe to maintain free way speeds with a slite incline in the road in 5th gear with the 33 X 10.5s WITH THE STOCK GEARS?
OCTANE DOESNT HELP YOUR JEEP, this isn't a high performance motor. Run 85 or 108 octane it'll be the exact same. People need some lessons on what octane does and when it's needed.
The only exception is for some people who are geared wrong lug the motors and are maybe pulling a trailer, even then 89 octane is more then enough.

United States

#45 Apr 21, 2011
I have a 2000 wrangler 4 clynder manual and get about13 15 miles per gallon i have had about 30 cars and trucks in my life but the one major thing about the jeep that cant be change besides being a box is the the old style engine it will run forever with a steel timing chain this is how all the old school engines worked and were very relibale no rubber timing belt to change. the simple fact is they were built for performence not gas milage and there is very little if anything you can do to change this . just try to enjoy your jeep chances are it will never leave on the side of the road. after all its a jeep and they wrote the book on fourwheel drive my 41 i will never forgetits just a jeep thing.
Sam the Mechanic

Kailua Kona, HI

#46 Nov 2, 2011
Vettegirl wrote:
I have a 2003 Wrangler X, 28,000 miles with the 4.0 and a 5 spd and I know it's not getting more than 15 mpg. I really thought it would get better than that since it's so small. I was VERY surprised and not in a good way. My husband is a car salesman and he says that most Jeeps get poor mileage. But I love it anyway!!
I have a 99 TJ, 4.0 5 speed, 151K miles, was getting 18mpg now 14 after 4 in lift 33's and more performance minded engine parts. I had a 2006 unlimited with 3" lift that got 18/20 with an automatic trans. i don't know what is wrong with everyones jeeps. best thing I found to help is throwing away the stock air intake and just making a new one with about $40 worth of plumbing parts and a conical filter. No they don't get great MPG but less than 18 for a stock 4.0 is crap and something is not right.

Winchester, KY

#47 Mar 19, 2012
You can get better milage,I get 24 with my 2000 Sahara,but it's expensive and you have to ask your self is it worth it.I have an easy $2000.00 dollars invested.first off it's addictive whwn you get get a little better mileage then you think I can get starts with a cold air induction kit,then you up grade the alternator to 160 amps and the battery cables to 0 gauge.then the alternator feed cable to 4 gauge.that way you eliminate voltage drop to the ignition system.syn oil is a good way to go but don't forget the trans or differentials and transfer case.I even did my power steering pump.then exhaust headders,the jeep ones are good, but they are just a tube exhaust manifold. you want a tuned equal length headder with a flex coupling so it won't crack under help that I used poly urathane motor mounts.then a free flowing exhaust system with a new cat converter,I used a dyno max converter.the last thing a good power chip that can be programed for ecomomy then set for performance when you want I said you can get caught up in this.yeah I get 24 mph but the extent I went to,I wouldn't do it you have to keep an eye on the spark plugs.I guess I'd just look at the tail pipe if it's sooty it's running too rich,if the dealer says it's not,ask around to other Jeepers what they did to clear it up. that will improve your milage some.with out throwing your vehical on the analizer thats the best I can tell you.Tommy

Stafford, VA

#48 Feb 11, 2013
I had a 92 jeep cherokee laredo 4.0 inline 6 auto with 33's on it, it got terrible gas mileage.. but then again im 16. its breaking down and i want a mid and late 90's cj . How much gas mileage does/might it get? Im possibly thinking of changing the air intake and maybe gears if i can afford it. Help?

Seattle, WA

#49 Aug 27, 2015
Jack wrote:
<quoted text>
If you drop 4.56 or 4.88 gears in it, you're milage is only gonna get worse. Right now, if your 4.0 Wrangler has stock diffs, they're around 3.07-3.10...I wouldn't recommend anything steeper than 3.73 or you can kiss your fuel goodbye. The minute you put a lift and oversized tires on a Wrangler, your fuel economy is shot on the freeway. It's shaped like a cinder block to start with, and now you have added to your drag on the undercarriage exposure. Running a 3.73 will help you utilize the power band more effectively, but the best improvement you can make for mileage is pretty spendy. You drop a chevy smallblock in place of the 4.0. My 92, 7" lift, 35's 4.0 Wrangler would get about 12mpg hwy... since the conversion to a 300bhp 350, I get about 20.
Did you need to swap out anything when you put the 350 in it? Do you think that engine would fit into my 00' Sahara?

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