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Thread: Improve Hemi Gas Mileage?

  1. #1

    Default Improve Hemi Gas Mileage?

    Has anyone done any mods or have any tricks to improve the 5.7 hemi's gas mileage?

    I'm getting about 11+ around town with normal driving. If I use cruise control a lot and baby the gas pedal I can squeek out low 13s. Highway driving seems to be between 17 and 18 mpg.

    I cringe every time I see the commercial about MDS improving gas mileage.
    2006 WK Overland. 5.7 Hemi, Dark Kakhi. - Magnaflow Catback, K&N Air Filter, Cabin Air Filter

  2. #2
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    trade it in for a prius, its a jeep, with a hemi nonetheless, what did you expect?
    2004 wj limited v8 h.o.

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    I wonder if anyone else has the same experience as me. For weeks I will putt around, trying to get every last bit of fuel economy, then I can't stand it anymore, and enjoy the HEMI's power, and the Jeeps handling. I drive with ernest, flogging the gas, and being amazed at the power available in a Jeep. Then for no good reason I fall back into the fuel economy mode...Jekyl and Hyde.

  4. #4
    Registered Yamsi401's Avatar
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    Why bother owning a Hemi Jeep if you don't exercise her ponies? I figure if I can afford a Hemi I can afford to keep her fed with 89 octane oats.
    Steve
    Abilene Texas
    "My JEEP ain't no SUV and your SUV ain't no JEEP!!"

    22+ years in a JEEP
    '84 XJ Cherokee Chief 2.5 I4 (traded for the '86)
    '86 XJ Pioneer 2.8 V6 (#2 Son's twice fully submerged and still runs)
    '97 ZJ Laredo 4.0 I6(#3 Son's)
    '01 WJ Limited 4.7 V8 (traded for the '04)
    '03 WJ Laredo 4.0 I6(traded for the '05)
    '04 WJ Overland 4.7 HO V8 (traded for a '06 Chevy 2500 Duramax 4x4)
    '05 WK Limited 5.7 HEMI (my lovely wife's) every option minus the navigation

  5. #5

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    Thank you for some of the BS remarks. :sadpink: But this is a real question.

    My point is, Jeep States 14 City / 19 Highway. The DCX commericals pump MDS as "fuel saving". It's close, but no cigar.

    IF mileage can be approved, then why would you NOT want to do it? Noone has an issue with increasing horsepower

    Yes, I enjoy the Hemi. Yes, I enjoy the Power. Yes, I like to hear the Magnaflow roar. Yes, I love to drive my GC.

    BUT, mileage is not as stated and I ESPECIALLY do not enjoy giving more $$s to the bloated profits of the oil companies than I have to.

    Why would you want to spend more on gas than you have to? If you were independly wealthy you most likely wouldn't be driving a Jeep and definitely wouldn't be hanging out on these forums.
    2006 WK Overland. 5.7 Hemi, Dark Kakhi. - Magnaflow Catback, K&N Air Filter, Cabin Air Filter

  6. #6

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    Your mileage around town does seem a bit low. I get around 14 in town and 18-20 on the highway. But like the others said, don't expect good gas mileage in any Jeep.

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    I average between 12-13 mixed driving. Maybe the government got a ringer when they tested!! The only thing that seems to help mine is to go really light on the pedal. If you keep that MDS on as much as possible (avoid all but subtle acceleration) you should see a nice improvment, maybe 2-3 mpg. That is if you can stand to drive it that way. If you drive in traffic, your screwed though.
    '06 WK 5.7 HEMI LMTD
    3" OME MD
    255/75/17 BFG MT
    4xGuard Matrix
    4xGuard Front Skid
    Rola Roof Rack
    Custom 3" catback with Flowmaster 40
    Airaid CAI
    4500K HID Upgraded Lowbeams
    4" Kragen HID Driving Lights
    Flashpaq

  8. #8

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    I get around 11 in town. You're not going to get the EPA stated mileage these are atested on a track in ideal conditions.

    Personally I have the split personality thing going on as well. I worry about the mileage and then I enjoy the 360 horses I've got under the hood (done some mods).

  9. #9

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    Im not sure there is any way to increase the gas mileage. I also get anywhere between 11 and 14 in the city usually high 12s or low 13s. On the highway I get around 16-17 if I keep it under 75 or 80mph. I wish the MDS would kick on higher than 60 mph when you are just cruizing on the the highway. I agree its frustrating to see the commercials and the EPA ratings much higher than reality. But I just keep enjoying that HEMI !!!
    2005 Grand Cherokee Limited HEMI
    Modifications: Maganaflow S/S Muffler & Catback system, K&N Air Filter, Airaid MIT, Chrome Fuel Fill Door, SRT-8 Pedals, Overland Grill, Overland Console, PIAA Headlights, 9005 Silverstar Ultra Fogs
    1997 Wrangler Sahara
    Modifications: 31" BFG ATs, Air Intake, Hella Headlights, Silverstar Fogs
    1989 Wrangler Sahara
    Sold: 1998 Grand Cherokee 5.9L Limited, 2001 Cherokee Sport, 1987 Wrangler Laredo

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    Quote Originally Posted by JEEPHEMI 5.7
    I wish the MDS would kick on higher than 60 mph when you are just cruizing on the the highway.
    I have heard my MDS kick in at 80 before under light loads. Problem is with CA traffic, I can never mantain a constant speed over 65 to experiment. At least not in the last 2 weeks I have had the car!!
    '06 WK 5.7 HEMI LMTD
    3" OME MD
    255/75/17 BFG MT
    4xGuard Matrix
    4xGuard Front Skid
    Rola Roof Rack
    Custom 3" catback with Flowmaster 40
    Airaid CAI
    4500K HID Upgraded Lowbeams
    4" Kragen HID Driving Lights
    Flashpaq

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    Quote Originally Posted by JEEPHEMI 5.7
    Im not sure there is any way to increase the gas mileage. I also get anywhere between 11 and 14 in the city usually high 12s or low 13s. On the highway I get around 16-17 if I keep it under 75 or 80mph. I wish the MDS would kick on higher than 60 mph when you are just cruizing on the the highway. I agree its frustrating to see the commercials and the EPA ratings much higher than reality. But I just keep enjoying that HEMI !!!
    My thought is that the whole fuel mileage debate is magnified by the fact that the WK has a small tank. Nothing like pulling over every 250-300 miles for fuel. Larger tank, less trips to the pump.
    Nothin Runs like a Jeepe!
    Two Black with Grey interior Jeeps
    '08 JK X, AUTO, Hard TOP. Finally!
    '06 WK limited 5.7 L Hemi, NAV,Tow, Side Bags U Connect, SRT Pedals. Satisfied Jeep Warehouse Customer
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    '99 TJ 4 banger. It hurts to talk about it anymore-
    [SIGPIC][/SIGPIC]

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    The official mileage numbers quoted have little or no connection to reality.

    The data are gathered while the vehicle is undergoing EPA emissions testing on a dyno.

    You'd think they'd measure the amount of fuel consumed and the miles "traveled" and simply divide the former by the latter. And you'd be wrong; there's something in simplicity and directness that abhors a bureaucrat.

    As incredible as it sounds, they actually infer fuel mileage by measuring tailpipe emissions and cranking the resulting numbers through some fallacious equation.

    Bottom line-- mileage numbers on the window sticker are worthless. There's not much the EPA gets right. And don't get me started on CO2 emissions.

    Now, having written all that, it's a mystery to me why the Hemi can't get at least a little better mileage.

    Larry

  13. #13
    Registered NightTrain's Avatar
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    Start off slow, maintain a steady speed and don't punch it.

    I've tried all the above and get around 14 in the city and have gotten 19-20 on the highway at a steady 65 mph cruise.

    As stated before, if I'd wanted good mileage, the last thing I'd have bought would have been this Jeep I'm enjoying. Once in a while, I'll enjoy the power of all 5.7 liters as I open it up at WOT on a nice stretch of road.

    Want great mileage? Get a Prius.
    '05 Bright Silver Grand Cherokee Limited
    5.7 liter "Hemi"
    Flowmaster exhaust
    Airaid CAI
    20% tint front windows
    SRT8 roof rails
    Debadged


    [SIGPIC][/SIGPIC]

  14. #14
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    The Hemi definitely is a powerful engine that should not be expected to be a super lightweight on gas mileage. However, getting in the LOW teens in city driving or metro commuting is something unexpected. For years big, heavy vehicles like Tahoes, Suburbans, full-size pickups, Durangos with 5.9L engines, etc. have gotten better mileage (14-16) with similarly large engines and older, less efficient technology. A 2005 Jeep with an 'advanced' Hemi sporting MDS should be able to do better. Unless you really drive with your foot in it, you should be able to get 15-16 around town consistently. I used to with a 4.7L WJ and a 300HP 4.6L Lincoln Aviator that was heavier. Sure, low-teens mileage isn't a whole lot different, but it is enough to matter. And yes, you can throw around all the disparaging comments about how we bought it knowing it was a powerful Hemi and paid a ton so a little more gas isn't a big deal, but the fact is there is just no valid reason for the 11-13 MPG that a lot of folks see. They aren't towing things, the vehicle isn't overly heavy (compared to Tahoes and pick-ups and Durangos), and most folks aren't driving it like its a race car. If we want to complain about it and look for ways to make it better it is our perrogative. I wasn't looking for a gas miser when I bought the WK Hemi, but I was disappointed to have worse gas mileage than I've ever had from a SUV that is smaller, lighter, and similarly powered to the last one I had (Aviator).

    And yes, having a few more gallons in the tank would help a bunch. I'd rather pay more at the pump than be at the pump more often.

    Rob
    2005 WK Limited in Midnight Blue, 5.7L Hemi, 4x4 Off-road, towing, 25K package, plus a few more options

    2001 Lexus IS300, loaded, Spectra Blue Mica

    Honda VTX 1800C cruiser - the most fun of the three

  15. #15

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    If it makes you feel any better, my 4.7 V8 WK doesn't do any better with mileage, so the HEMI is definitely more efficient than the 4.7
    '05 WK 4.7 4x4 Midnight Blue Grand Cherokee Laredo - X Package - Walker Quietflow SS

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    First off, who drives 65? Around the Bay Area, or at least where I drive, everyone cruises 70+ so MDS will virtually never kick in for me and I only get 16 mpg on the highway.

    Those who mentioned having a larger gas tank are right! why do you think they have slightly increased the gas tank for next year...

    Here is the question:

    IF MDS DOES KICK IN and I'm cruising at 60 mph- what gas mileage show I get: 18 mpg...20....25???

  17. #17
    5.9 Elitist ptownTSI's Avatar
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    i got 13-14.5 mpg city in my 5.9 if i drove it reasonably. and 20mpg freeway if i kept it 65.

    dont go over 65, try to "time" stoplights so you are not coming to a stop before they turn green again, so you arent wasting momentum that you had to use gas to build up. dont go over 2000 rpm's around town. dont try to pass people alot, this does nothing but waste gas as you will probably end up meeting them at the next light anyways.
    98 5.9 Limited (my 2nd 5.9 and 3rd ZJ)
    Ice cream paint job
    Rear view mirror, Jumbo dice! Trunk hit hard like Kimbo Slice.

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    I have began to drive slower and keep it easy, but I would rather have fun driving my jeep, not worrying about burning an extra gallon because I had to pass a guy.



    Botton line, I guess there is really nothing we can do- I see it as a big engine that is "full time" 4x4. The 300c gets much better mileage with its hemi right?

  19. #19
    Registered Yamsi401's Avatar
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    Quote Originally Posted by ddrouin
    Thank you for some of the BS remarks. :sadpink: But this is a real question.
    My point is, Jeep States 14 City / 19 Highway. The DCX commericals pump MDS as "fuel saving". It's close, but no cigar.
    What haystack did you just fall off of? EPA estimates not close to actual mileage? STOP THE PRESSES!!!

    Quote Originally Posted by ddrouin
    BUT, mileage is not as stated and I ESPECIALLY do not enjoy giving more $$s to the bloated profits of the oil companies than I have to.
    Since the archive has been lost there's no sense but to say that this has been hashed out several times before. Here's a summary of some facts:

    1) The price of oil is not set by the "bloated" oil companies but by the various market drivers like the Chicago Board of Trade. Oil is a commodity like gold or coffee and the price is set by speculators based on many factors like China's unending appetite for crude, the production capability of the oil producing nations, and the apprehension of the individual speculator.

    Here in Texas in 1985 when the oil market went bust and the cost of oil was worth less than the cost of the barrel we put it in nobody complained. Congress made no effort to help out the industry. Same happened in the late 1990s when the Asian market was in a depression and Singapore and Japan had no demand on oil and again gas prices were low. But when the price goes high - watch out!!! GOUGERS!!!

    All oil producers do is suck the oil from the ground and sell it based on external forces. If they also refine the oil into other products they're hit with the lack of refineries (last US refinery built in 1976) and regulations from the various markets that force extra costs to the consumer. Ask how much fuel tax the New York motorist pays per gallon some time.

    Quote Originally Posted by ddrouin
    Why would you want to spend more on gas than you have to? If you were independly wealthy you most likely wouldn't be driving a Jeep and definitely wouldn't be hanging out on these forums.
    MDS kicks below 65 MPH and is at its best between 60-65, check out WKJEEPS.com and read all about it. Again, here in West Texas the speed limit is 80 MPH in Interstate 10 and 20 so going 65 MPH is out of the question. I have hit 20 MPG on long stretches of East Coast highway where the speed limit was 65 MPH. You can feel the MDS kick in and out

    Fuel prices are part of the cost of ownership. If owning the Hemi powerplant (or the 4.7 it seems as well) makes it tough on your budget then perhaps it is time for you to focus on a more economical vehicle. If filling your tank makes you cringe you'd really scream paying my truck's Diesel bill. Get over it.
    Steve
    Abilene Texas
    "My JEEP ain't no SUV and your SUV ain't no JEEP!!"

    22+ years in a JEEP
    '84 XJ Cherokee Chief 2.5 I4 (traded for the '86)
    '86 XJ Pioneer 2.8 V6 (#2 Son's twice fully submerged and still runs)
    '97 ZJ Laredo 4.0 I6(#3 Son's)
    '01 WJ Limited 4.7 V8 (traded for the '04)
    '03 WJ Laredo 4.0 I6(traded for the '05)
    '04 WJ Overland 4.7 HO V8 (traded for a '06 Chevy 2500 Duramax 4x4)
    '05 WK Limited 5.7 HEMI (my lovely wife's) every option minus the navigation

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    Quote Originally Posted by rx7dan
    If it makes you feel any better, my 4.7 V8 WK doesn't do any better with mileage, so the HEMI is definitely more efficient than the 4.7
    See, that's not right either. The 4.7L in our old 2000 WJ used to average around 15 in around town driving. The WK isn't THAT much heavier.

    Rob
    2005 WK Limited in Midnight Blue, 5.7L Hemi, 4x4 Off-road, towing, 25K package, plus a few more options

    2001 Lexus IS300, loaded, Spectra Blue Mica

    Honda VTX 1800C cruiser - the most fun of the three

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