2006 Jeep Commander 4x4 Hemi TERRIBLE GAS - JeepForum.com
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post #1 of 6 Old 12-08-2009, 06:37 PM Thread Starter
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2006 Jeep Commander 4x4 Hemi TERRIBLE GAS

We recently purchased a 2006 Jeep Commander 4x4 Hemi. The information center says we are averaging 8.5 mpg is this normal? If it is not normal what can we do to improve gas mileage.


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post #2 of 6 Old 12-08-2009, 07:32 PM
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Abnormal from my viewpoint. Should be ~13-18mpg city/highway. I typically get 16-19mpg rural / highway driving in the '08 GC Limited.

First, check your mpg the old-fashioned way: miles driven/gallons used. Mine compares favorably (95%+), but not exactly. Another 5.7L HEMI GC Limited owner told me that his system behaves the same way. This check at least establishes whether or not your electronics are performing properly.

You didn't state mileage or maintenance status, but spark plugs, air cleaner, and correct oil do a lot for HEMI mpg.

Champion 570 copper plugs ONLY for mine, every 30K miles. Verify this is the same for your model year. Apparently, these 5.7L HEMI's are very particular about spark plugs. Do not accept platinum "upgrades". Lots of bad stories by other forum members here. You can read more at XKJeeps.Com and probably even download a pdf of your owners manual.

Other stories on this forum tell how dealers have incorrectly used 10W-30 oil in the HEMI. The MDS function works on 5W-30. If MDS isn't functioning, your mpg will drop drastically. Since I couldn't tell exactly what was used and my MDS was acting up, I changed fllter/oil myself to a K&N oil filter and Castrol Syntec (full synthetic) 5W-20 oil. It helped.

Final area to look at is the back side of the throttle body. Elsewhere on this forum, 90grandoneer has helped us with the oil crud that builds up on the back side. There are even some before / after pictures by another Commander owner. Worthwhile endeavor. Use a mild solvent to clean the crud, like alcohol. These intake throttle bodies are specifically listed by Chrysler as not being serviceable, yet we see stories that dealers will take >$160 to do a throttle body cleaning. IMHO, I wouldn't go for it.

If you do the work yourself, all of the above will cost you ~$75 in parts and 2-3 hrs labor. Be interested to hear about your results.

'08 WK GC Limited. 5.7L HEMI. Quadra-Trac II. Bright Silver Metallic. Class IV hitch.
Michelin LTX M/S tires. Fumoto oil drain valve. Billet Technology oil catch can.
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post #3 of 6 Old 12-08-2009, 07:42 PM
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Originally Posted by jayz151 View Post
We recently purchased a 2006 Jeep Commander 4x4 Hemi. The information center says we are averaging 8.5 mpg is this normal? If it is not normal what can we do to improve gas mileage.

There's a thread on Jeep Commander Forums: Jeep Commander Forum that addresses real world gas mileage in Commanders:

Real world gas mileage? - Jeep Commander Forums: Jeep Commander Forum

I averaged 17.83 in my Commander over the first year; six cylinder, auto, 7 seat option. Mixed driving, city and highway, mostly city.

8.5 seems a bit low, even for a hemi engine. Most seem to be hitting 12 or better, I think.



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post #4 of 6 Old 12-09-2009, 09:17 AM Thread Starter
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post #5 of 6 Old 12-12-2009, 07:09 PM
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as simple as this seems, have you tried resetting the system? our 2005 ram without mds gets at least 12 we don't drive like it's stolen but we don't go easy either, you might be interested in a predator, DiabloSport :: Gas and Diesel Tuning Systems you can adjust your settings and it can run live diagnostics, JEEP - 2006 - SummitRacing.com that link also shows the trinity, which is the newest tuner from diablosport, DiabloSport :: Gas and Diesel Tuning Systems fine tuning your settings can help mpg
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post #6 of 6 Old 12-13-2009, 11:24 PM
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Are you running ethanol mix or real fuel? That'll make a big difference. e85 even bigger. But around here, all the real-gas places switched down to that 10% crap... can't even find real fuel anymore and that makes a huge difference on the MPG. Example, my bike gets 65MPG on real gas, riding hard and two-up and fast and all that. On the 'standard' 10% crap they now serve, if I get 50, I'm overjoyed. I usually get mid 40's going a bit slower and solo even (which bikes tend to get their best mileage in that situation).

If the norm for the Hemi is 12 and you're getting 8-9, that's about the same difference as I see (up to 30%) with just the fuel differences... Most people see 10-20% differences but each engine and situation is different. Don't feel bad, my TJ with all it's armor and fat tires and what not can get down to 6 if I put my foot in it.

Simple things to keep the MPG up; Keep your tires properly inflated (you can lose 5-10% in this alone. Slow down a bit can save you more than you'd think. The fuel burn difference from doing 60-65 to 65-70 can surprise ya. Then ofcorse no jack-rabbit starts or full-throttle passes. In my non-aerodynamic Jeep, I keep it at 60 (65 on the big super-slab) or less. If I watch everything and drive careful, she can get 16... That's a huge difference.

Just some things to think about and consider. Your rig might be fine. It might just be the fuel mixed with driving habits and vehicle configuration. It's possible.

And if you're running e85 (can that engine? I think so), then that would actually be good fuel mileage. I hate e85... but that's another topic.

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