How to get better fuel milage?

[Live For God]

I would like to get better fuel mileage in my 1988 Jeep Comanche that has a 4.0 liter engine and a 4 speed auto transmission

I currently get 15 M.P.G. driving to and from work

Any help would be appreciated

:D :wrench:

[JENSSEN]

Get a 4 banger 5 speed, I get 36mph highway,..

 

Won't ever win a race but,... Lol

 

Start with tune up parts , and go from there

[FrankTheDog]

Go gentle on the accelerator. The difference between me driving like I like to and driving like there is an egg on the pedal is at least 3 mpg.

[cruiser54]

Yep. Either take this advice, or get a used Honda Civic.

[Pete M]

yup, tune her up to like-new and drive like you've only got 3 teaspoons of gas left in the tank.

 

what size tires do you have?

[mpace6a]

In my old chevy i flipped it in nuetral and coasted...alot. Do it enough and you'll start finding places where you can coast well over a mile without losing speed. helped conserve gas when i only got 8mpgs...Also when i started finding places like that, just kill it, but turn the key back to the "on" postion and you'll still be able to steer.

[Pete M]

it is NOT recommended or condoned to turn off the engine. you lose power steering and brakes and you'll want both of those in an emergency. :thumbsup:

[JeffN]

install a vacuum gauge and try to keep the needle as high as possible

[ratrapp]

thats all i get is about 15mpg.the truck sticker only showed like 18mpg when brand new so losing 3 mpg after 200k miles isn't too bad.i also think the only way you'll get better mileage is to get another vehicle.some people claim high fuel #s for 4.0s and such but i attribute this to poor math,inaccurate speedos and such.maybe a 4.0/5spd 2wd and easy driving may net 20mpg or so but thats another story.i base my 15mpg on a combo of city and highway(not highway only)and routinely gets this every week.i also have a 4.0 aw4 with 3.55s and 235/75/15 tires and a correct speedometer as i changed the gear to get it right.

[mpace6a]

Thus far, power steering hasnt been a problem, and actually you still have power brakes as long as you keep off the brake pedal and only use it if absolutely necessary. But anymore I don't have to kill it, my ram randomly dies on its own. And the engine light never stays on long enough to make it to oreillys to check it :(

[terrawombat]

Get a 4 banger 5 speed, I get 36mph highway,..

 

Won't ever win a race but,... Lol

 

Start with tune up parts , and go from there

 

36MPH on the highway? Sounds like a hazard.

 

Assuming you meant 36MPG on the highway, then I'm thinking your speedometer is reading very high, which is causing your presumed miles/tank to also be high. The only engine offered in the XJ/MJ that could possibly achieve those numbers would be the Renault diesel.

 

To the OP - if you truly want to get better fuel mileage that will actually make a noticeable difference, you would need to turn your truck into a 2WD 5-speed with stock (or smaller) wheels/tires and the smallest gear ratio rear end you can find (3.07 or below). When I got my 2WD 4.0L 5-speed with stock rims, I averaged 23.5MPG on a trip from OH to NJ doing 65-70MPH. It was a lot of downhill driving so I'm sure that accounts for the higher than normal numbers. As soon as I put a slightly larger set of tires on the truck, my MPGs went down to 18.5/19 on the highway.

[Automan2164]

Driving habits. I drive like an old man and can get my 5300 lb ZJ with the 4.0L into the low 20's consistently. I never drive above 60, the cruise is always on, and I coast well before I know I have a stop coming.

 

Drive like you don't have a brake, because when you brake, you are basically throwing out the mileage/fuel used to get up to that speed. Easy up, easy down... I like the idea of driving with a vacuum gauge and keeping it on the high end... Never thought about that I guess.

 

Rob

[mvusse]

Thus far, power steering hasnt been a problem, and actually you still have power brakes as long as you keep off the brake pedal and only use it if absolutely necessary. But anymore I don't have to kill it, my ram randomly dies on its own. And the engine light never stays on long enough to make it to oreillys to check it :(

 

If the check engine light has been triggered, even if it's a minor intermittent problem causing the light to go off again, the error code should still be stored in the computer for the next 50 key off/key on cycles.

 

Take it in whether the light is on or not.

[Automan2164]

Thus far, power steering hasnt been a problem, and actually you still have power brakes as long as you keep off the brake pedal and only use it if absolutely necessary. But anymore I don't have to kill it, my ram randomly dies on its own. And the engine light never stays on long enough to make it to oreillys to check it :(

 

If the check engine light has been triggered, even if it's a minor intermittent problem causing the light to go off again, the error code should still be stored in the computer for the next 50 key off/key on cycles.

 

Take it in whether the light is on or not.

 

 

 

It depends on the type of code. Some don't set history codes... Some take more faults to set, some take less, some get cleared by such and such conditions. I think, depending on the year of Mopar, you should be able to flash the codes through the odo whenever you want.

 

I would imagine that if its enough to kill the truck though, something would be stored...

 

Rob

[JENSSEN]

Get a 4 banger 5 speed, I get 36mph highway,..

 

Won't ever win a race but,... Lol

 

Start with tune up parts , and go from there

 

36MPH on the highway? Sounds like a hazard.

 

Assuming you meant 36MPG on the highway, then I'm thinking your speedometer is reading very high, which is causing your presumed miles/tank to also be high. The only engine offered in the XJ/MJ that could possibly achieve those numbers would be the Renault diesel.

 

 

 

Distance traveled was via GPS and I was following the posted limits keeping the RPMS low

[mpace6a]

Thus far, power steering hasnt been a problem, and actually you still have power brakes as long as you keep off the brake pedal and only use it if absolutely necessary. But anymore I don't have to kill it, my ram randomly dies on its own. And the engine light never stays on long enough to make it to oreillys to check it :(

 

If the check engine light has been triggered, even if it's a minor intermittent problem causing the light to go off again, the error code should still be stored in the computer for the next 50 key off/key on cycles.

 

Take it in whether the light is on or not.

 

 

 

It depends on the type of code. Some don't set history codes... Some take more faults to set, some take less, some get cleared by such and such conditions. I think, depending on the year of Mopar, you should be able to flash the codes through the odo whenever you want.

 

I would imagine that if its enough to kill the truck though, something would be stored...

 

Rob

Its a '97. Last time i took it up to check, the light went off as soon as I pulled in the parking lot :doh:

They went ahead and tried to read it anyway, and all the popped up was a seatbelt code?

[terrawombat]

Distance traveled was via GPS and I was following the posted limits keeping the RPMS low

 

Eh, then something is amiss. Else wise you have the most fuel efficient 2.5L AMC engine on the planet...and not even by a little bit, but by a long shot. I've seen plenty of people tossing around numbers in the 24-26MPG range from that engine, but 36...that's quite a jump.

[AMCJeepMJ]

 

 

Distance traveled was via GPS and I was following the posted limits keeping the RPMS low

Eh, then something is amiss. Else wise you have the most fuel efficient 2.5L AMC engine on the planet...and not even by a little bit, but by a long shot. I've seen plenty of people tossing around numbers in the 24-26MPG range from that engine, but 36...that's quite a jump.

I have tracked my 2.5 on fuelly.com http://www.fuelly.com/driver/oceanic815/comanche and am averaging 19.5 at current. Highest mileage for a tank I have received is 22.0 mpg. This mileage is with a canopy on the bed, the truck tuned up, fluids changed regularly, tires properly inflated and wheels aligned, no A/C, shifting early so it almost lugs down, and doing a maximum of 55 on the highway. This is with a 4-speed manual.

The mileage I am receiving is about what the EPA says I should be getting according to the chart from the cash-for-clunkers campaign. I'm hesitant to believe regular claims above 25 mpg in a similar rig... a one-way trip from the mountains to the coast or living somewhere very flat such as southern Alberta, yes- over the course of several months, no.

 

June 2014 edit:

 

I was able to hit 25 mpg for two tanks in a row in May 2014; to do this, I did not exceed 50mph [unless coasting downhill], shifted early, started coasting to a distant stop very early [1/8 to 1/4 mile [more on hwy], had my tires aired to maximum sidewall [50psi], empty bed, no canopy, did almost no city driving [highway only], and was very light on the gas pedal while accelerating.

 

However, for the guys with the 33" tires doing 80 stating they get 25mpg, I call BS.

[terrawombat]

I have tracked my 2.5 on fuelly.com http://www.fuelly.com/driver/oceanic815/comanche and am averaging 19.5 at current. Highest mileage for a tank I have received is 22.0 mpg. This mileage is with a canopy on the bed, the truck tuned up, fluids changed regularly, tires properly inflated and wheels aligned, no A/C, shifting early so it almost lugs down, and doing a maximum of 55 on the highway. This is with a 4-speed manual.

 

The mileage I am receiving is about what the EPA says I should be getting according to the chart from the cash-for-clunkers campaign. I'm hesitant to believe regular claims above 25 mpg in a similar rig... a one-way trip from the mountains to the coast or living somewhere very flat such as southern Alberta, yes- over the course of several months, no.

 

Words are wind and people like to boast bold claims, but the truth of the matter is that both the 2.5L and the 4.0L engine are only capable of so much, in terms of MPG, and I become extremely skeptical when that numbers creeps above the 25MPG mark.

[mvusse]

4 cylinder, 5 speed, 3.55 gears (not 4.10 like the 5 speed is supposed to come with) I get 27mpg cruising 60 mph. Doesn't matter if I'm in 4th or in 5th. Makes me think if I slow down a bit (55 mph or so) in 4th gear I might eek out 28mpg.

 

Cruising 75 in 4th gear (before I had a 5th) I got 19mpg, in 5th I get 24.

 

Current average mixed mileage (over 11,000 miles) is 20.28.

[johnj92131]

First, pump up your tire. Pressure. This will lower your rolling resistance.

 

Second, 2 wheel drive only.

 

Third, slow down. Be gentle with acceleration. Drive as smoothly as you can.,

 

I have hit 23 nog on the highway with my 4.0 automatic, but get 17 around town.

[mountainman]

so far since putting my manche together i have put about 1000 miles on her.

I'm getting 19-21 mpg.

I did an LA trip last weekend and so i did the mileage/consumption test. (only real way)

Go by point to point mileage vs how many gallons used.

So i filled it to the cap and drove. 270 miles and used just under 13 gallons.

Bed loaded full of stuff (700 lbs or so) and no cruise control (havent fixed that yet)

5th gear most of the way and 4th on the hills (baker grade) AC on the entire way.

Avg'd 75 mph.

 

quick hijack... what gears do i have. I have an 8.25 (ID'd by the great axle thread on here) and at 70 mph i run 2k rpm. 215/75 15" tire. 75 is like 2100 rpm.

 

Thanks for any info gang. Dave :wavey:

[landlubber]

 

quick hijack... what gears do i have. I have an 8.25 (ID'd by the great axle thread on here) and at 70 mph i run 2k rpm. 215/75 15" tire. 75 is like 2100 rpm.

 

Thanks for any info gang. Dave :wavey:

 

you might glean some information from HERE about your ratios, or if all else fails, remove the diff cover and it will be stamped on the pinion gear.

 

 

to the topic of fuel mileage, I get around 12-14 city and somewhere in the very low 20s on the highway, 2wd, skinny tires, and a light foot is the key, for most of us mpg's go out the window with big knobby tires and heavy bumpers and driving styles.

[vaquaro]

This topic always comes up concurrently with gas prices :yes: Regarding Jennsens post , probably converted to Imperial gal.( 10% more than US gal.) , roads /hiways around Calgary are mostly flat and maintained better than any where else in Canada , the man obviously keeps his trucks in good repair/tune . ....Here on the Wet Coast I commute 40 km each way to work , about 50% hiway & 50% stop and go city ,complete with steep hills . Winter mileage 13.5 litres/100 km (20.8 mpg ) , Summer 12.5 l/100 km (22.5 mpg ) Strait hiway @ 100kph + 11.5 l/100km (25.5 mpg ) , Strait hiway @ under 100kph 10.5 l/100km (26.8 mpg ) . I should add my hiway drives are usually mountainous , using 3rd gear often to climb the steeper sections . That,s my $0.02 :cheers:

[jimoshel]

Walk?