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My MPG is embarrassing to mention.

7K views 40 replies 22 participants last post by  John_R 
#1 ·
I have a '05 WK V8 RM 55K and everyone is good except the MPG. Right now I'm getting a shameful 7.8 MPG city and if I jump on the highway for 10 miles It may go up to 10-11MPG.

I had the fuel injector cleaned and some crap the oil change people told me I need to clean in the engine and nothing has changed. I would like to know what can I do to improve the fuel consumption. I got the car 13 months ago and the MPG has always been pathetic but now I cant take it anymore.

I'm not a mechanic so I really cant do anything myself so odds are I'll take it to a shop and even worst the dealer. Thanks everyone but if I can just get 13MPG city I will be okay because I'm seriously thinking of trading the car in for a GMC terrain.
 
#3 ·
Fuel efficiency has never, EVER been a Jeep strong point. You're in the wrong make of vehicle to be concerned with that. I'd hate to see you flip to the dark side, so on to your problem...

The single greatest factor in poor gas mileage is driving style. Obviously heavy acceleration, stop and go, lots of city driving, etc. will kill your mpgs. Be honest, you have a V8, so you drive it like one, eh? ;) You really have to drive it like a granny to get any decent mileage. I don't know if it's changed, but back in the day, mpg's were calculated on a track with a test vehicle traveling 45 mph in a VERY controlled environment. I thought I had read somewhere the government is demanding more realistic estimations.
 
#4 ·
My 426 gets somewhere around 10-11MPG in combined city/highway driving so something may be off. How many miles do you have on the Jeep? Have you checked/changed the air filter? Spark plugs? The gas you are using can also play a role.
 
#11 ·
Is this the Hemi? If so, are you using regular (87) or plus (89). IIRC the manual calls for 89 octane fuel. You can run 87 in it, but this will result in reduced performance and fuel economy.

The estimates I see are 15/20 for the 4.7, and 14/19 for the Hemi assuming 4x4. You are not too far off if you had an SRT8 with the 6.1, but some other things to check would be as follows:

-Tire pressure - Generally speaking your fuel economy suffers about 3% for every 1psi below spec. My 08 calls for 33 and the standard now is 35psi. I run slightly higher at 37psi.

-Brakes/parking brake - Check these items. Sticking brakes or a mis-adjusted parking brake will kill your mpg and ruin your brakes very quickly.

-Ditto the plugs and filter. IIRC Jeep does not use the platinum (100k change interval) plugs in these vehicles....but don't quote me on that.

Also, like was stated driving style has a lot to do with MPG. Constant speed changes and excessive brake usage will result in very poor fuel economy.
 
#12 ·
Check the plugs,air filter,pcv valve,make sure the oil grade is 5w20-it is required for the engine to run properly. Get a CAI intake and magnaflow muffler or whatever you like,the biggest holdback is the huge factory muffler on these. These will all help with your mileage.
 
#13 ·
im thinking it is your driving style. plus the evic tells you the mpg's over the last 30 miles so jumping on the highway for only 10 miles is not going to do much. you seem to drive too much city. but even so i have never had lower than 13mpg in the city so im guessing driving style.
 
#14 ·
Wow, CG4x4.. I did a pricing on what u mention and just the muffler and CAI came to over $1K. For that I can take it to the dealer to probably get a complete tuneup for cheaper.

It's a 4.7 V8 non HEMI rocky mountain with 55K miles. I've switched the synthetic oil 9 months ago. I got brand new tires with proper inflation. I drive the car when I'm working about 6 miles a day total and probably around 40-50 miles a week total.

There probably isn't nothing wrong with the car though because 4 months ago I drove the car from NYC to Toronto and got 22MPG. I wish it had stated at 20 but it came back down to earth. So that's why I'm inclined to think the car just may need a tuneup.

I think I'll try with the plugs,air filer and PCV valve first to see if it makes a difference.
 
#16 ·
Look on eBay for the CAI and Muffler, I got my CAI for less than $70 used and my 1286 24 inch magnaflow muffler for about $80 bucks. My friend just spend $800 on his FJ cruiser for a similar setup and was like:eek: when I told him what I paid, I installed the CAI myself and for the muffler,all I did was trade the old cat from my 99 WJ to the muffler shop for the muffler install.:D
 
#15 ·
Just curious....how are you calculating your average mpg? This is all in-town driving? Are you carrying any extra weight like gear or other cargo? Is the suspension factory (un-lifted)? Any luggage or other racks on top? Any over-sized or off-road tires? Has the alignment been checked?

With the 4.7 your numbers should be higher than that.
 
#18 · (Edited)
The stop and go plus short trips are just killing it. Its to be expected. I agree with the fact that your Jeep is running just fine. Especially when you got a 22mpg est. economy on the highway. I drive way more than you in one day to work, almost 70 miles round trip a day, then you do in a entire week. If anyhting I should be trying to look at a more efficient vehicle. I love the Jeep and its not going anywhere right now. Besides why would i or you for that matter want to get rid of the Jeep... take a loss on it... and then start a brand new car loan on a new vehicle. I hope i'm not being rude but, trading in the jeep in your situation is penny wise and dollar foolish.
 
#19 · (Edited)
Which V8 is it? 5.7 or 4.7? I have the 4.7 and i get 12 city and 18 highway on average keeping it below 75 on the highway and not racing to every stop light. The worst i have ever had was 10 and i was just having fun and thats nothing compared to some of the other guys on here with lead foots, SRT8s and having fun.

I have no intentions of getting a more fuel efficient vehicle any time soon. If anything it would be a hemi jeep or ram.
 
#20 ·
with my new SCT tuner and Sean tune Ive been getting 8 mpg's....LOL. But it could be my large size 14 right foot.......
 
#24 ·
if you only drive 6 miles a day to work the engine barley even gets time to warm up properly...in the manual it says to drive at least 15 miles to get the fluids warmed up when checking the trans fluid so I would assume its safe to say it takes at least 15 miles of driving to get the engine and fluids at the ideal operating temperature.

You can try starting you car 5-10 min before you leave for work so it gets a little extra time to warm up. See if that helps out at all.....if not try replacing the spark plugs and air filter
 
#28 · (Edited)
Damn guys! And here I used to complain about my 25 mpg @ 80 mph in my 400 hp (stock) GTO :D and yeah ,that thing had power!

Seriously though, I don't feel bad now getting ~15 city/19 hwy in the WK...chrysler vehicles never get good mileage for some reason and single digit is pathetic if you think about it - especially with only 400-hundred something HP and a relatively small efficient engine and overdrive...I understand weight, but that is disgusting mileage and glad I didn't opt for the SRT, ouch(even my chevelle with its thirsty 383-450+ hp carb'd engine with no overdrive that wasn't tuned (running badly) got low double digits)
 
#29 · (Edited)
Funny that you mentioned... I was gonna bring up the same point. My 04 GTO is getting around 16/22 on 93. Its a 5.7 with some bolt ons and a mild tune.

Kind of bummed to read this as Im currently looking at getting a jeep with a hemi and was hoping to use it as a daily... Was hoping it would at least be in 20s hwy.
 
#33 ·
Important point is idling. Idling will affect your overall average because when you are sitting idle you are getting 0 mpg.
Idling doesnt really affect your mpg as much as you would think. For example, according to my mpg reader on my gto, it only consumes about .5 of a gallon per hour at idle. Maybe about .8 with ac on.

But I think coasting does. On hwy if you speed up to say 75 and then let off gas and coast until you slow down to 70 and repeat the process. I've noticed a slight increase (about 2mpg) in doing this vs keeping speed constant. Dont have a jeep yet so cannot comment on it but I would assume it would work the same way.
 
#36 ·
Towing close to max for my 4.7L doing 70-75, I got 12mpg.

Even in city driving with mileage tune or 87 oct performance tune using 89 OCT (stuff with 10% ethanol) I get 15-17. Those tunes on the highway doing 70-75 I get nearly 24.

I have a AFE stage 2 intake, 180* tstat, and superchips tuner.
 
#38 ·
Even with stop and go traffic I would still think my MPG would be in the double digits. Haven't gotten around getting the plugs change yet so will see after later this week. I calculate my MPG by the inboard computer. I have a remote starter in the car and I don't use it because it lowers my MPG even more. Everything in the Jeep mechanical is all stock. No mods nothing. On a brighter note

I test drove a new Hyundai Tucson "don't laugh" and they would cover what I owe on the jeep but I didn't sign. Will be checking out the GMC terrain this week to see if I can get a deal on that. a

Also considering buying a small car and keeping the jeep..
 
#39 ·
Even with stop and go traffic I would still think my MPG would be in the double digits. Haven't gotten around getting the plugs change yet so will see after later this week. I calculate my MPG by the inboard computer. I have a remote starter in the car and I don't use it because it lowers my MPG even more. Everything in the Jeep mechanical is all stock. No mods nothing. On a brighter note

I test drove a new Hyundai Tucson "don't laugh" and they would cover what I owe on the jeep but I didn't sign. Will be checking out the GMC terrain this week to see if I can get a deal on that. a

Also considering buying a small car and keeping the jeep..
I don't laugh at Hyundai/Kia anymore. They are nowhere near the joke of a car company they started out as. I would still wait. 2011, ALL American Hyundais and Kias are getting major facelifts.
 
#41 ·
Yeah, I briefly considered a 2010 Genesis Coupte R-spec (2.0 T 6-speed) and it was a nice vehicle, good mileage and fair price (~$24k), but it was a little small for my current needs [be a great commuter though)...Thing wasn't super powerful (V6 is supposed to be, but you're looking at $30k+), but has a lot of potential and comes with some real good equipment (like brembo brakes, LSD, etc.).
 
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