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Unread 11-14-2002, 09:15 PM   #1
agcamaro
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Gas Mileage

Has anyone considered putting in a lower gear ratio to help with the horrible gas mileage on the 4.7L grand cherokees? I know it has enough power to push it along at lower RPM's and wonder if anyone has done it. I dont know what ratio I have in it now.

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Unread 11-15-2002, 06:31 AM   #2
Intrepidjeep
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Please believe me, you've got the best compromise they could find for all-round fuel efficiency, driveability and performance.

Fuel economy is a sticking point on the Jeeps. Chrysler wanted that vehicle to get the best possible gas mileage without hurting all-round performance and driveability too much, so they had to compromise.

Considering that a gear ratio swap would cost upwards of $1000 unless you did it yourself, you'd have a long wait to ever make up the cost of the rear axle change, and I doubt you ever would.

Meanwhile you'd be dealing with slower acceleration, more frequent downshifts at ever incline in the road, and other annoying traits of a vehicle that's geared too tall.

Honestly, the biggest single factor in fuel economy is DRIVER habits. Very moderate use of the gas pedal at all times, selecting routes that allow you to cruise more often, cruising at lower speeds all help. If you have the trip computer that shows you instantaneous gas mileage, that will help you to get significantly better mileage -- far more significant improvement than changing your axle ratio. Using good brands of gasoline (Chevron, Shell, Amoco, Texaco) that have good fuel detergents in them. Actually a
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Unread 11-15-2002, 08:09 AM   #3
agcamaro
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I drive it like its a baby. dont ever jump on the accelerator at all. I just cant believe how I can actually notice the gas needle move after only driving to the store and back. I guess when you take into consideration how much you pay to get lower gears, it will come out to be the same with the extra cost in gas in the long run. Thanks for the advice.
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Unread 11-15-2002, 03:19 PM   #4
Intrepidjeep
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Do you have the trip computer that gives you average fuel economy? Reset it next time you fill up the tank and see what the average is.

In my mixed driving with the 4.0L, I get about mid-17's. Highway cruising at maybe slightly over 70mph, it'll get 21mpg.

I'm sure you didn't buy that GC for its fuel economy, so just kinda put the issue away and enjoy the vehicle for its awesome good looks, performance and heritage. That's what I do, lol. Oh, and, if possible, drive the 'other' car when you take long trips -- we use our '98 Intrepid ES 3.2L, which can cruise on the highway at 74mph and still get 30mpg.
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Unread 11-15-2002, 05:18 PM   #5
ALS59LTD
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If you want better gas milage why did you spend the extra money on a V8 in the first place? trade in for the inline 6 if you are concerned about gas mileage.
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Unread 11-15-2002, 07:33 PM   #6
agcamaro
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I am getting about 17.5 mpg on my trip odometer. I guess I am just used to my camaro that got awesome gas mileage. When I bought it, I didnt research it enough to know how it did on gas. I just knew I wanted the exta power. After what I have read, I dont think I will ever buy the I-6 in the Jeep. I test drove one once and then the V8 and there was no comparison. I guess its just something I have to get used to.
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Unread 11-16-2002, 10:23 AM   #7
Intrepidjeep
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Remember, too, that a Jeep or any other offroad-capable vehicle really needs a bigger, low-rpm, high-torque engine for offroad use -- you have to be able to do a slow crawl over large obstacles.

The 4.0L inline 6 was good for offroading for that reason, and it was cheap to produce. It's really 60's technology, though, with a real good multipoint EFI system added and some minor refinements otherwise (lightweight aluminum rods and pistons, roller rockers, roller timing chain, improvements to the combustion chamber and elsewhere, etc.). But it's still old tech. That engine will be out of production very soon. They phased out the Cherokee and replaced it with the Liberty, which uses a much more efficent V6. (Of course, the Liberty weighs about 600lb more than the Cherokee, so they ended up with little or no better gas mileage as a result, go figure.)

That 4.7L is much newer design from the oilpan up, so that helps to offset its larger displacement and give it practically the same fuel efficiency. Since the second-gen GC is larger and heavier by a good amount than the first-gen, that makes it tough, too.

I imagine the other models like the GC will get that new engine to replace the 4.0L completely.

To hell with fuel economy -- give me that new 5.7L Hemi engine in a Grand Cherokee!
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Unread 11-18-2002, 10:46 AM   #8
Lowboy
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I've been averaging 15mpg in the city and around 22 on the highway/freeway. I would consider that pretty good mileage for a vehicle of it's weight and engine size.
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