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  #13  
Old 12-24-2010, 10:26 PM
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Re: gas mileage? 4.0 what can i do?

01 4.7 and I routinely get 15mpg no matter how I drive though my area requires mostly stop and go driving.Not sure what you were expecting when you bought yours but my hopes were to get around 17 mpg.
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Old 12-24-2010, 11:08 PM
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Re: gas mileage? 4.0 what can i do?

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Originally Posted by boosted88coupe View Post
Oh and we only run 93 octane gas... its easier that way... I have some high strung toys and they always get better mileage burning the premium fuel
Sometimes running 93 may hurt, not help the problem. See what you get running 87. Worst case is that you get the same gas mileage and save some money.
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  #15  
Old 12-24-2010, 11:35 PM
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Re: gas mileage? 4.0 what can i do?

I have an 04 4.0, just hit 128,800 today. I have had it for just about a year now. The best MPH I have gotten according to EVIC was 16.0, and that was during the spring. I haven't seen that again since. I am currently at 15.5, it's normally around 15.6 or 15.7. I have been trying to accomplish some better mileage too, although many people have told me it's not a big deal, you have an all wheel drive SUV, you're not going to get good mileage. I have seen plenty of people on the various jeep forums posting way better mileage then I have gotten. I also been logging my mileage up on the fuelly.com website that Marcus uses also. And according to that my mileage is worse then what the EVIC shows. I changed my plugs over the summer and that didn't make a difference as far as I can tell. I drive 25 miles each way to work on the highway, and also stop and go and city driving too. I took the jeep on 200 or so mile highway trip a few months ago, and mileage proved to be around the same, doing 65-70 mph. A few other long trips and nothing to write home about. My bank 2 1 02 sensor was replaced as I got a CEL for it during the summer. I have though about replacing the other 3 also. And even changing the fuel filter. Some have said not to touch it unless it needs to be replaced, and others have said replacing it makes difference. I also changed my air filter to a k&n drop in filter over the summer.
here is my page on fuelly
http://www.fuelly.com/driver/mrjaydeeone/grand-cherokee
and that one great mpg of 19.8 was right before I did the long highway trip and I filled up just to go on a full tank, and I only needed 6.5 gallons
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Old 12-25-2010, 12:26 AM
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Re: gas mileage? 4.0 what can i do?

Quote:
Originally Posted by Joe's2001Laredo View Post
01 4.7 and I routinely get 15mpg no matter how I drive though my area requires mostly stop and go driving.Not sure what you were expecting when you bought yours but my hopes were to get around 17 mpg.
I was hoping for high teens low 20's not 14...

I am an ase certified auto mechanic... cleaner is better when it comes to premium fuel... I don't buy 87 period... I have a 5.0 thunderbird with over 300,000 miles and it has had nothing but premium... and is still on the original injectors... I have never replaced an injector on my cars do to it going bad. I am gonna toss some dimes at the jeep if it doesn't get better its going down the road.
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  #17  
Old 12-25-2010, 09:47 AM
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Re: gas mileage? 4.0 what can i do?

Quote:
Originally Posted by boosted88coupe View Post
I was hoping for high teens low 20's not 14...

I am an ase certified auto mechanic... cleaner is better when it comes to premium fuel... I don't buy 87 period... I have a 5.0 thunderbird with over 300,000 miles and it has had nothing but premium... and is still on the original injectors... I have never replaced an injector on my cars do to it going bad. I am gonna toss some dimes at the jeep if it doesn't get better its going down the road.
Since you're a mechanic you should know that the higher the octane the slower it burns (as it has less heptane). Unless you bump up the timing on your 4.0L, you're making less power on an already underpowered engine. Engines that are tuned for higher octane either have higher compression (not the case here) or increased timing to give the fuel more time to ignite.

If you're concerned about fouling injectors, run sea foam through the fuel every 6 months. It's basically injector cleaner that's used at most shops.

BTW, what transfer case do you have? I have Select Trak so most of my driving is done in 2wd.
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  #18  
Old 12-25-2010, 09:55 AM
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Re: gas mileage? 4.0 what can i do?

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Originally Posted by mrjaydeeone View Post
My bank 2 1 02 sensor was replaced as I got a CEL for it during the summer. I have though about replacing the other 3 also.
I think you only have 2 on the 4.0 1 before and 1 after the cat and the rear 1 doesn't have anything to do with engine operations it just monitors how well the cat is working though it will throw a code if bad.
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OK, fine...I'll admit...some amber lamps are good, and necessary.
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  #19  
Old 12-25-2010, 10:17 AM
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Re: gas mileage? 4.0 what can i do?

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Originally Posted by boosted88coupe View Post
cleaner is better when it comes to premium fuel... I don't buy 87 period...
I've seen many instances over the years where people have lost 1 to 2 mpg running premium fuel(usually on lower performance engines). I think JeepMe is on the right track. Some motors don't respond well to premium fuel and the 4.0 might be one of them. Our 99 has 220k on it and has always run the cheapest junk i can find with no issues. Also as Knightrider03m said winter blend gas always causes a decrease in mileage. Usually about 1.5 mpg every year for me on both the 4.7 and the 4.0. I think i'd give a tank of 87 a try and see what happens.
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OK, fine...I'll admit...some amber lamps are good, and necessary.
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  #20  
Old 12-25-2010, 07:50 PM
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Re: gas mileage? 4.0 what can i do?

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Originally Posted by cheapjeep View Post
I think you only have 2 on the 4.0 1 before and 1 after the cat and the rear 1 doesn't have anything to do with engine operations it just monitors how well the cat is working though it will throw a code if bad.
oh okay. I guess it dependso on cali or fed spec 1 has 2 1 has 4
taken from www.wjjeeps.com

so whatelse can be done for some better mpgs?
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Old 12-25-2010, 08:01 PM
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Re: gas mileage? 4.0 what can i do?

How accurate is the lil display on the ceiling in the jeep, because according to that im only getting 12.9 mpg. I have a 2000 4.7 with 120,000 miles, any ideas.
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  #22  
Old 12-25-2010, 10:25 PM
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Re: gas mileage? 4.0 what can i do?

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Originally Posted by scrivenerc View Post
How accurate is the lil display on the ceiling in the jeep, because according to that im only getting 12.9 mpg. I have a 2000 4.7 with 120,000 miles, any ideas.
I don't think it's all that accurate. If you look at my post above and click on my fuelly link and check out the average mpgs it says I get. The display has never gone lower then 15.5 and never above 16.0
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  #23  
Old 12-25-2010, 10:53 PM
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Re: gas mileage? 4.0 what can i do?

Quote:
Originally Posted by mrjaydeeone View Post
oh okay. I guess it dependso on cali or fed spec 1 has 2 1 has 4
taken from www.wjjeeps.com

so whatelse can be done for some better mpgs?
Pardon my French but that just goes to show how retarded Cali is about their emissions that they actually need 4 O2 sensors on a single exhaust. That's just f'in insane!
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OK, fine...I'll admit...some amber lamps are good, and necessary.
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  #24  
Old 12-25-2010, 11:22 PM
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Re: gas mileage? 4.0 what can i do?

Quote:
Originally Posted by scrivenerc View Post
How accurate is the lil display on the ceiling in the jeep, because according to that im only getting 12.9 mpg. I have a 2000 4.7 with 120,000 miles, any ideas.
IMO they're pretty conservative in that I've run them 0 miles left for 20 miles and still had a couple gals left in the tank. Keep in mind though there's gonna be a big variance from vehicle to vehicle.
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OK, fine...I'll admit...some amber lamps are good, and necessary.
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