how can i get better gas mileage?

[hoobness]

I used to get 270-280 miles to a 20 gallon tank. Then all of a sudden it dropped to 200 - 220 when winter began.

Locals around here said it was winter gas. Winter is over now, and the mileage has not improved.

I have also since then added 33 x 12.5 MT/Rs and 4" of lift. I understand the tires will take the gas mileage away... with the tires its down below 200 miles to a 20 gallon tank! I think there is something wrong.

BTW its got a weber 32/38 ( i was getting good mileage for a year with it)
Ford TFI upgrade from this site...

I have replaced the plugs, fuel filter, leaned it out, checked the air filter, reduced the fuel pressure (it was leaking out of the float bowl), re timed it, it idles at 600 rpm, very smoothly, it has headers, high flow cat, pacesetter muffler, and 2.5" tailpipe..

All emmisions tubes are gone, only have PCV and vacuum adv. no EGR etc.

What should I look for, < 10 mpg is killing my wallet with $2.15 gallon gas!

help!!

[Robrt-Stephens]

Originally Posted by hoobness

I used to get 270-280 miles to a 20 gallon tank. Then all of a sudden it dropped to 200 - 220 when winter began.

Locals around here said it was winter gas. Winter is over now, and the mileage has not improved.

I have also since then added 33 x 12.5 MT/Rs and 4" of lift. I understand the tires will take the gas mileage away... with the tires its down below 200 miles to a 20 gallon tank! I think there is something wrong.

BTW its got a weber 32/38 ( i was getting good mileage for a year with it)
Ford TFI upgrade from this site...

I have replaced the plugs, fuel filter, leaned it out, checked the air filter, reduced the fuel pressure (it was leaking out of the float bowl), re timed it, it idles at 600 rpm, very smoothly, it has headers, high flow cat, pacesetter muffler, and 2.5" tailpipe..

All emmisions tubes are gone, only have PCV and vacuum adv. no EGR etc.

What should I look for, < 10 mpg is killing my wallet with $2.15 gallon gas!

help!!

The answer is in your tires and lift.

[Bounty__Hunter]

Two answers are in your tires and lift. You're likely not geared correctly in the axles, and the engine has to strain much more than it used to. You've also gained quite a bit of frontal area by lifting the jeep and adding larger tires, you know push a lot more air than the rolling brick used to.

Other things to consider are:
Optimal tire pressure
Driving habits, slower acceleration and 10mph less top end will save a lot of fuel

Keep in mind that your odometer is now off since the installation of larger tires, it's reading fewer miles than you're actually driving.

[ujohnd]

Buy a Honda!

[Snitty]

if you get the right speedo gear, you'll notice you're actually getting more. and that 2.15/gallon is pretty cheap

[hoobness]

I understnd the lift and tires are a factor.

however I was getting 270+ to a 20 gal tank until october-novmber.. then it dropped drastically to around 220. The lift and tires have only been on there for a month.

so besides the height mods and tires, i think there is something wrong..???

[Bounty__Hunter]

I listed many factors:

• Increased front profile of the jeep is less aerodyamic
  larger tires strain the engine, keeping it below the optimal rpm range
  speedo/odometer error gives the appearance you're getting worse mileage than you really are.

I'd bet that's the extent of it. Larger tires and lift didn't just affect mileage one way, but at least three.

[felix_santi]

Try running 2 ounces of acetone in your tank for a couple fills. Besides the cleaning effect, you should notice a difference, I did.

[Bounty__Hunter]

I've read a lot of good things about acetone, several in my club have tried it with great results. I think they saw a few threads on it over at NAXJA. They talk like a 2-3mpg increase.

[Snitty]

I should try that

[lah2420]

Did it get good mileage with the TFI or did it start going downhill after the TFI? Also, did you replace the PCV valve? Not sure how much that would affect mileage, but it sounds like you are going to have to hit it one step at a time. Also, check that your carb or adapter plates haven't loosened off. Mine loosened at the bottom plate and would pull just enough air that it ran richer. Also, check your intake/exhaust bolts. Don't overtighten. Get a torque wrench and make sure they are torqued down. Most are about 22 foot pounds, but 2 of them are somewhat less. I can't remember what though. Again I had a problem there.

[laneiac]

I dont think there is anything you can do to the engine thats going to get you back where you were. Its all in your gearing and tires.

[TwistedCopper]

I don't think it can be stressed enough that your odometer is way off and you actually have no idea what kind of mileage you are actually getting.

Change the speedo gear and go from there.

[currupt4130]

there was a recent article on pirate about putting acetone or something of that nature in your gas tank, like 12oz per 20 gallons, apparently itll boost it like 4 or 5 mpg, not sure but you might want to do a search on it over there and see what you come up with. i think it was in general chit chat. it was fairly re cent

[LVRockCrawler]

you could come out here to vegas and pay $2.50/gal for regular.... no.. go on the intersate and check the odometer against the mile markers (or have someone pace you at several different speeds) to figure your speedo error since the lift - mine is about 10% w/the 33's - that and the lift may explain the lost mileage... still better than my freightliner at 6mpg loaded!!! hope i helped!

[Bounty__Hunter]

It's more like 2oz. per tank of fuel IIRC. Better check it out before adding anything.

[felix_santi]

like he said, @ 2oz per...
http://pesn.com/2005/03/17/6900069_Acetone/ http://www.pirate4x4.com/forum/showt...hlight=acetone http://www.lubedev.com/smartgas and a couple more links in the pirate site..

happy trails

[Spatula]

2.65/gallon of regualr 87 octane gas in the San Francisco bay area.

Other than acetone, xylene will give you similar results as an additive to your normal pump gas. Certiainly, first things first, and get that spedo gear changed out. I just bought a used '01 TJ Sport w/ 4" suspension lift, 35" tires, dana 44 rear end, 4.10 gear ratio. I haven't put it thru the paces enough quite yet to determine actual gas mileage, but at this point it looks like its getting a minimum of 10+ mpg.

Larger tires will cause your axels to spin at a slower speed, throwing off your speedo and tripometer, registering less miles driven per tank which will cuase your MPG to be off. One wrong number in the equation, causes the wrong result.

Other things that can affect gas mileage are roof racks or roof mounted lights. Try to find a fairing to divert the airflow over these if possible. Or, you could buy something used that gets 30+ mpg, and write the price off as gas savings. Think long term.

[mcon12000]

It's the tires and lift for sure. I've got a 2000 TJ with 33's and I'm getting about 11-14mpg on the freeway. My speedo has been regeared to show the correct speed so my mpg are accurate. The next move for me is a gearing change to get my engine rpm back within it's ideal operating range. My stock ratio is 3.07 and I'll need to go to something like a 3.83 to correct for the tires. Even with the gearing change I don't expect to get the same milage as before but it will improve. Has anyone done the gearing change after living with the stock ratios on this site that can report on the actual gains in mpg?

[Bounty__Hunter]

Welcome to Jeepz.

No such ratio as 3.83 for Wrangler axles, but there is 3.73 and 4.11. For 33" tires and 3.07 gears I'd go with 4.11 to get your performance and mileage back. 3.07 to 3.73 isn't enough of a change to warrant the time, money, and trouble.