Jeep Commander Forum banner

1 - 15 of 15 Posts

·
Banned
Joined
·
6 Posts
Discussion Starter #1
I'm sure there are a ton of threads on this, but the ones I have searched seem to pull more up on the 4.7. I'm test driving an '06 Limited Hemi 5.7L with 138k miles. The vehicle looks like they put it on a dyno for the last 10 years straight and went to lunch. I can't believe how clean the inside/outside is so I'd REALLY love to buy it, but seriously concerned about fuel use. I've reset the MPG info twice now on the trip computer, and I'm consistently getting 8.9 to 9.9 on the average. Is this something I just have to accept, or is there something wrong. I know it's all time 4x4 and a 5.7 Hemi, but was hoping for better than 9mpg average. Thanks!
 

·
Premium Member
Joined
·
629 Posts
My 06 - 5.7 gets around 14 in the city and as high as 21 on the highway if you have a tailwind:)
More typical is 14 city and 17 highway, it is very close to the same as the 4.7 as the 5.7 has MDS - Multi Displacement System where it shuts off 2 cylinders under light load (stead speed on flat road or downhill) But it is a HEMI and my foot likes it too much. With that low mileage it probably needs a tune up or putting in the correct oil - 5W-20.
 

·
Super Moderator
Joined
·
5,710 Posts
I don't have a Hemi, but I think that's kind of low - even for a Hemi.

Maybe the spark plus need to be changed - or the fuel system/injectors might need to be serviced/flushed.

I'd asked the dealership - or the person you are considering buying it from, if they have a good vehicle maintenance history that they can show you - that would help eliminate some of the potential causes.

This has nothing to do with the mileage but I would also check underneath the chassis and give it a good once over for rust.

I've seen used SUV's that look really super-clean from the outside - until you crawl underneath them and look.
 

·
Banned
Joined
·
31 Posts
I actually have a HEMI in mine, unlike others that have commented. With a lift and 265/70/17 tires, I've averaged 13.1mpg after 750 miles of mixed city/hwy driving. I do have a K&N air filter in mine. If you do the 7% correction for the tire size difference from stock because I haven't reprogrammed the speedo, that puts me at 14mpg on 87 octane gas. Before I lifted it, on stock tires, I reset the mpg. I would average about 14mpg, but if you sat at a stop light very long it would tick down. Read somewhere that the MDS shuts down 4 cylinders at driving speed under 65mph. I included a picture that gathered info on 2006/2007 and calculated approx. mpg average over 1 million miles and 100 owners.....13.2-13.3 mpg average. If you're worried about gas mileage, go buy something else. My buddy has one with a HEMI with the 255/75/17 tires, which have a 9% speedo correction, without a K&N filter and he's averaging 12.6 on 89 octane after correction. He just swapped out the air filter, so we'll see how much difference it really make.
 

Attachments

·
Premium Member
Joined
·
294 Posts
I just looked at the average mileage on my wife's 2010 Hemi XK that goes 7.5 miles one way to work and it said 16.4, though it has new plugs about 5,000 miles ago, fresh 5/20 full syn. oil and clean stock air filter. So at this point I feel pretty lucky.

Swanny
 

·
Banned
Joined
·
6 Posts
Discussion Starter #6
Thanks all. I did purchase it because it was a great deal, so I'm going to get it to my tech next week for a complete tuneup and I'll post how it does!
 

·
Registered
Joined
·
65 Posts
Best of luck to you. Mine will not average over 15 on the highway with the air on and 10 in town. This is the main complaint I have with this truck. I hooked an led light into the mds system and am appalled at how little it even functions. It mainly turns on under real slow speed driving or downhill. It dis-engages with even the thought of any uphill.
 

·
Registered
Joined
·
1 Posts
Mpg

I have a 2006 with 84000 miles. Hemi 3.73 gears, and I get 11.3 in the city. I really only drive it around town.
 

·
Banned
Joined
·
6 Posts
Discussion Starter #9
I also have the Diablo I2012 on the way, so I'll let you know if I gain any MPG from some of the installed tunes.
 

·
Registered
Joined
·
17 Posts
13-14 city, and I have seen as high as 19 on a tank with all highway driving at moderate speeds without any wind. 8-9 seems quite low unless you are drag racing at every stoplight.
 

·
Premium Member
Joined
·
136 Posts
2008 Hemi Limited Quadra Drive II

12 or 13 city never better than mid 15's highway 78 MPH here in MI typically. New plugs, full synthetic, new diff. fluids, new WIX air cleaner. The 5 speed while very durable is not the most efficient. My MDS system works reasonable well IMO. If you increase the viscosity of oil it may affect the MDS system I am told.
 

·
Premium Member
Joined
·
629 Posts
paluztv Change the oil to a 5W20,. who knows what the previous owner put in, If oil change was done by a quick change company it probably has the wrong oil. The MDS kicking in and running on 4 cylinders does not like anything other than 5W20. And if you want to see if the MDS is active add a LED that will come on when MDS kicks in. See how to add it here. http://www.jeepcommander.com/forums/10-electronics-nav-discussion/10433-m-d-s-what-how-do-i-know-when-active-5.html See post # 45 on page 5 where they start the addition of the LED indicator.
 
1 - 15 of 15 Posts
Top