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Discussion Starter · #1 ·
I've got a '99 Wrangler 4cyl, that I'm only getting about 15 mpg with currently. I know that Jeeps are not known for great gas mileage, but I never realized that it was THIS bad....
I'm looking to sell my car, so the Jeep is about to become my daily driver. I'd like to improve my fuel economy fairly soon since I'll be driving across town 5 days a week. Any ideas on what my first step would be?

FYI: I did a tuneup last year and the engine is stock.
 

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i get 19-22 with mine. have to ask-lifted and big tires on it? that and the way you drive plays alot into it. i don't really get on it(much :) ) is stock and has stock tires on it.
 

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I've got a '99 Wrangler 4cyl, that I'm only getting about 15 mpg with currently. I know that Jeeps are not known for great gas mileage, but I never realized that it was THIS bad....
I'm looking to sell my car, so the Jeep is about to become my daily driver. I'd like to improve my fuel economy fairly soon since I'll be driving across town 5 days a week. Any ideas on what my first step would be?

FYI: I did a tuneup last year and the engine is stock.
What size tires and which transmission are you running?
 

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Discussion Starter · #4 ·
I've got 31x10 50R15 tires and 5-speed manual transmission.

I usually don't get on it, except for the occasional merging on the freeway kind of thing.
 

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I'm only getting 14mpgs and I have the 4.0 running 33x1250, tires are deffinately playing a part in it I would run some fuel injector/carb cleaner through a couple tanks of gas and see if that helps
 

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I would run some fuel injector/carb cleaner through a couple tanks of gas and see if that helps
Fuel injector cleaners, even the very good Techroline, pushed by the autoparts stores are a huge scam. Why? Because virtually all grades of today's modern gasolines have more than enough fuel injector cleaning additives already added to them. That wasn't always the case, especially when fuel injection was relatively new, but it is today. In fact, I used to have 20-30 car & truck dealers as clients & I used to shoot the bull with the mechanics once in a while. A question I always asked them was how many legitimately clogged fuel injectors they had seen while working on their customer's cars, Jeeps, & trucks. The older guys always said it had been years since they had seen one, and the newer guys would always say never. That's why those fuel injector cleaning services pushed hard by dealer service writers is also a huge scam that is something like 90% pure profit for them.
 

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When I change oil I put 1/2 cup of Sea/Foam in the tank . It,s very good in Chain Saws and weed/eaters .

BANGER
 

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i was getting 12mpg in my 4 cylinder automatic, its up to 14 after i changed out a bad o2 sensor. i have been told that a TPS or IAC could be some of the problem. BtW my jeep is stock with stock rims and tires
 

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Discussion Starter · #10 ·
Most injector cleaners are alcohol-based, so why do they advertise alcohol-free gasoline as being better??
Oh well, I don't use them anymore. I heard that they and alcohol based gasoline are bad for vehicles, so I quit using them.
 

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Any check engine light? Have someone with a scantool check your coolant temp. If the temp isn't 195degF, the eng runs in "open-loop" mode and therefore, very rich. Check the operation of your thermostat, and/or replace it. Secondly, tall tires on the 4cyl eng will simply kill your fuel economy. I changed my thermo and our economy went up dramatically.
 

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Discussion Starter · #13 ·
Any check engine light? Have someone with a scantool check your coolant temp. If the temp isn't 195degF, the eng runs in "open-loop" mode and therefore, very rich. Check the operation of your thermostat, and/or replace it. Secondly, tall tires on the 4cyl eng will simply kill your fuel economy. I changed my thermo and our economy went up dramatically.
Nope, no check engine light on. The only time it has come on was when I think I got a bad tank of gas. I ran that through, and at the next fill-up, it was fine.

I'm really wanting to upgrade to a 6cyl eventually (once I have a 2nd car again for a daily driver), so I hate to spend a bunch of cash on things like cold air intakes and such, especially for an engine with over 100k miles. I would consider it though, if the benefits would be good enough to tide me over until I can afford the engine upgrade. Anyone know of someone selling a used CAI for a 4cyl??
 

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A CAI is not going to help improve fuel economy in the slightest... not one iota. Not that it would help mpg but even if it did, which it won't, how long would it take to recoup the CAI's costs through any expected fuel savings? A loonnnnggg time. That's if the could help, which they don't.

And with the EPA and federal government breathing down the necks of all the automotive manufacturers to squeeze out ever possible .3 mpg, they would have gone to CAI intakes long ago if they actually helped with fuel economy. But they don't. Not in the least. :)
 

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And with the EPA and federal government breathing down the necks of all the automotive manufacturers to squeeze out ever possible .3 mpg, they would have gone to CAI intakes long ago if they actually helped with fuel economy. But they don't. Not in the least. :)
Actually all new cars do have Cold Air Intakes. They all have a hose to draw in outside air. They just don't do a fancy looking job of it with a curved aluminum pipe and a cone filter. Basically the reason why the aftermarket CAI's don't help mpg any is the factory designed stuff now adays isn't that bad.
 

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IDK ... I would say it is more a driving style ... I get 20mpg with a 4.o ... but i baby it big time to acheive that ....
 

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yea I was getting 21 with my old 4 cyl
 

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Oh yeah, on a 4-cyl. Wrangler with large tires, you're going to take a big hit in fuel usage. Everyone I know has the same problem. You don't get something for nothing.

Consider moving back to the stock tire and wheel size, install good quality dual-purpose tires and inflate properly. In the meantime, driving habits rule the day.

I always get 20+ in my 4.0 TJL, but I drive it like a baby carriage and shift at 1800 rpm. I usually skip 2nd gear around town as well, and time the lights well. You should see the angry, idiotic Road Rabbits who ROAR around me when I drive gently in town. I always catch them at the next red light just as it turns green, and smile as I slowly pass.

I'm glad I don't have their fuel bill.
 

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If you have a 4cyl with 31s, you are getting down on it all the time unless it is parked! If it always stays under 30mph would be the only way to take it easy on it.
Want fuel economy? Get a car. End of story. NO tj can possibly be fuel efficient, they are shaped like a brick, and have major turbulence under them due to being high off the ground.
If you wanted a fuel efficient tj with a 4 cyl, you would have to lower it to the ground, put tiny tires on it, hardtop, swap a cherokee 2wd beam front axle and trans into it, AND baby it. You could probably eke out around 25-27 mpg like that.
BTW, about impossible to put an actual cold air induction on a tj because they all suck hot air from the engine compartment. I guess you could make a scoop and ducting to gather air from under the front bumper, but with all the ductwork, it would probably make it worse than better. Colder air does make more power therefore better economy, but it is marginal and it would take a LOT of miles to recoup the cost of a $300 system by edging out an extra .5mpg.

EVer looked up the actual fuel $$ saving from a "fuel efficient" diesel truck? There a re a ton of people that never tow or haul and have a diesel because they claim better fuel savings. BUT, figure in how many miles you would have to drive to recoup the extra $8k for the diesel to break even. IIRC, it was around 140k miles before the new(read crappy mileage due to epa crap) diesels and with gas and diesel being equal cost, probably double that now that gas full sized trucks can get about the same or sometimes better mileage than diesel. Dont forget the oil changes costing at least twice as much and very expensive parts when somthing does fail.
My point is, if you want somthing fuel efficient, get somthing that was designed that way from the start, dont try to make somthing fuel efficient that wasnt meant to be. I dont think fuel efficiency was even on the list of design parameters for a pop top, solid axled, high ground clearance, 4wd jeep.
 

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little off topic but did a comparison on a different forum(RV) compareing my 8.1L against my bro-in-laws new diesel and doing the actual cost per mile etc opens your eyes--shut alot of ppl up when i shared my findings(ps-used my BIL's real numbers not the made up ones often tossed around) and that was just operational costs-no maint or cost of repairs. you could give me a diesel, but i'd turn around and sell it for a gasser.
will hunt it up(link) if anyone interested.
 
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