[Valkhorn]

I'm new to the forums here, so I joined today and was browsing around for information on improving gas mileage. At 2 bucks a gallon, and since I plan on one or two road trips this summer I have been thinking about what I can do to improve the existing 'stock' mileage on my Jeep.

I drive a 1999 Jeep Grand Cherokee Laredo. I bought it used this past December, its got 85,000 miles on it (11k of those put on since I bought it). It has solid metal brakes and brake pads, and as far as I can tell other than that its pretty much stock.

The current mileage is 15 city, and around 21 to 23 highway. I've looked up on the internet and talked to some people I know about improving mileage and so far they've suggested several options.

• Buy a turbonator and a K and N air filter
• Buy a new exhaust system
• Buy a new headers/spacers for the exhaust system

I'm definately not a mechanic and so I'm not sure if even the terminology is correct on this. All I know is I drive my jeep properly, I wash it regularly, change the oil regularly, and watch the tire pressure regularly.

I've also heard that the turbonator doesn't help much, if at all, and that it seems to be more of a gimmick. I suppose one does get what one pays for - as a new exhaust system and headers would cost a couple hundred dollars at least.

Also I wanted to purchase a new suspension system for my jeep because when I drive it for long periods of time I just want a better ride. Stock, it's ok, but I wouldn't mind the shocks to be a little stiffer when I have to deal with 15 hour drives on the road. Would new shock absorbers help much with mileage?

Thanks for your time. This is my first jeep, so I want to take care of it.

[EMTimZJ]

turbonator = a piece of bent scrap metal. Nothing will be gained by this "mod"

The K&N combined with a better exhaust set up would yield some pluses.

Make sure your plugs, wires and cap are good.

Make sure that your O2 sensors are in good shape. for your 99 WJ that has OBDII MOPAR O2 sensors are strongly recommened.

Also your MPG will be greatly affected by driving style. if you're aiming for a better mpg, go a little easy on the skinny pedal.

Good luck!

oh and welcome to the forum
we're a great bunch

[Valkhorn]

The K&N combined with a better exhaust set up would yield some pluses.

So we're talking 40 bucks for the filter, and around 250 to 400 bucks for the exhaust system. What kind of gains do you think I could get on highway mileage? If it's 21 now, would somewhere around 23 or 24 be reasonable?

Make sure your plugs, wires and cap are good.

Is there a quick way to eyeball them to make sure without having to drive it into some garage somewhere?

Make sure that your O2 sensors are in good shape. for your 99 WJ that has OBDII MOPAR O2 sensors are strongly recommened.

Allright, exactly how do I find out without taking it into a garage? Also, if I don't have them, how much would it cost to have them upgraded?

Also your MPG will be greatly affected by driving style. if you're aiming for a better mpg, go a little easy on the skinny pedal.

Good luck!

Thanks for the tips!

[porrsher]

valkem,
I take it you have the 4.0 L, if you are getting 15-23 thats awesome, to put it in perspective I get about 14-18.5 after changing O2 sensor on my quadratrac 5.2L.
and I take it easy on the skiny pedal.

[Valkhorn]

Yup, I'm getting 15/21 right now. Or at least thats what my mpg display thing tells me

I tested it out actually and during one trip I was averaging on the highway 380 miles for 18 gallons of gas.

[FPKites]

Probably be a good idea to throw some cleaners through it as well. Fuel system cleaner in the tank (I like BG44k, there's Chemtool and lots of others, whatever suits you), throttle body cleaner - pull off the airbox at the intake and spray it out real good cleaning the carbon deposits off. Less carbon=more air. Fuel injector cleaner - you can go all out and pour a bunch of gunk down the throttle body, let it sit, then fire up the engine and let it smoke it out. Take a look around for Seafoam, or you can look at my post on BG Fuel Injection System Cleaner.

A clean engine is a happy engine. I've gone from 15 to 16.5 average after last weekend's cleaning, and I haven't even gone through a full tank with the BG44k.

At 85k miles, sparkplugs woudn't be a bad idea.

[michiganmaveric]

I put on a K&N filter and a Flowmaster 50 Series muffler in March. before i installed these items I did a road trip from Michigan to Oklahoma and averaged 21.3 MPG with the cruise set at 65MPH. I just did the same trip with cruise set at 65 MPH and got 22.2 on my overhead but figured it out the old way (basic math) and found I averaged 22.5. The Flowmaster sounds a little ricey but who cares i fit will get better MPG. You can also clean your injectors. A lot of people becommend SEAFOAM, I personally use STP fuel injector cleaner in the black bottle. One of the biggest things is to slow down and go easy on the gas when taking off from a stop.

[greasefingers]

There is basically nothing one can do to improve mileage. As others have stated, keeping it tuned-up, is about the best thing for this. It really makes me laught when I see a product/device that claims to improve mileage.

[PlatinumZJ]

Whatever you do, don't count on modifications to help much with MPG, they typically help with horsepower and torque with a minor % increase in MPG. Typically a improved exhaust system that yeilds better HP and torque with a % or two better MPG will cost $800 to $1000 with installation (the $400 to $500 system will simply replace the existing with the same new stuff). The so called cold air intakes at $100 to $300 (or modifing the existing air box) are also required to get that improvement (say 10% better HP and torque and 5% better MPG). So you spend $1000 for the improvements. At $2.00 per gallon thats about 25 20-gallon tank fulls (6-months of driving for me). To get to a break even at 5% improvement (about $2 per tank), it will take about 500 tank fulls (~150,000 miles or ~10-years for me).

I have improved my MPG fro 14.5 to 16.5 (+13% in town) by simply easing off on the gas pedal (hardly ever reving over 2000 rpm), using cruise on straigh flat streaches, coasting to traffic lights, drivingf smoother, planning trips for efficiency, and avoiding the rush hour parking lots.

If you want mods for performance Go for it. But don't count on them for savings at the pump.

[Valkhorn]

Whatever you do, don't count on modifications to help much with MPG, they typically help with horsepower and torque with a minor % increase in MPG. Typically a improved exhaust system that yeilds better HP and torque with a % or two better MPG will cost $800 to $1000 with installation (the $400 to $500 system will simply replace the existing with the same new stuff). The so called cold air intakes at $100 to $300 (or modifing the existing air box) are also required to get that improvement (say 10% better HP and torque and 5% better MPG). So you spend $1000 for the improvements. At $2.00 per gallon thats about 25 20-gallon tank fulls (6-months of driving for me). To get to a break even at 5% improvement (about $2 per tank), it will take about 500 tank fulls (~150,000 miles or ~10-years for me).

I have improved my MPG fro 14.5 to 16.5 (+13% in town) by simply easing off on the gas pedal (hardly ever reving over 2000 rpm), using cruise on straigh flat streaches, coasting to traffic lights, drivingf smoother, planning trips for efficiency, and avoiding the rush hour parking lots.

If you want mods for performance Go for it. But don't count on them for savings at the pump.

Thanks. I never really thought of it that way

I do want to performance mod my jeep, and if I got better torque, horsepower, a better running engine, and it sounded nicer maybe it would be worth it.

But since it won't give me the improvements I desire - only for vanity purposes with mileage - maybe I should just spend money on better shocks first so I can start taking it off road a little more.

[EMTimZJ]

If you are looking for MOPAR O2 sensors, check around at your (pains me to say this) dealer... call around and see who has what for how much.

Then e-mail / call Nick Ianuzzi (most people refer to him as Kolak) for prices on the MOPAR O2 sensors

kolak@aol.com

Also, this THE person to talk to when it comes to exhaust and engine performace for your Jeep

[PlatinumZJ]

I want more torque and power, and porbably should look for a V8, but I have limited $s and have started down this path. Its hard to justify mods and such (especially to the wife ).

[Woody]

I have yet to see anyone who has modded their Jeep to get better MPG get enough to justify the money they spent on it. I think someone touched on it, but spending $400-$2000 on putting better equipment on it might get you only a 2 mpg gain, and a savings of $170 a year based on $2.00 a gallon and 12,000 miles a year. The skinny pedal is your friend, just don't bash him much and like someone else here said. It's not hard to keep the RPM's below 2000 for your in town driving and driving 65 on the freeway instead of 80. Using both of those two methods I get 15 mpg in town, and between 22-26 on the freeway. Remember I have a lifted Jeep with bigger tires, and overhead rack with spots, and the spare, and a few other items which are a bog. My 99 WJ bone stock never got better than 20 no matter what I did. It was an I-6, but I think it was a lemon, it had more problems than I ever wanted to deal with.

Save your money for gas. The only mods I plan on putting money into are those listed in the sig. Have a good one!

[SouLTeRRoR]

I put some fuel ingetor cleaner, and a K&N drop in filter. I'm up to 15.2 mpg and I have a heavy foot most of the time.

[cherokee04]

When I put in a drop-in foam air filter and went full synthetic from front to back, I was able to get the mileage up from 14/17 to 18/21, and I don't expect it to get much better than that with the weight and V8 engine.

I am glad to finally see gas come down a little now -- since I use 2 to 3 tanks a week. I still don't like $1.86/gal, but it's better than the $2.34 it was just a couple weeks ago.