I feel cheated

[jamesqf]

Originally Posted by bandit86

the display showed as 23- 24mpg instant on the highway on the test drive. thats what IT, the car itself promised.

Maybe your test drive was downhill, or you had a good tailwind?

Or maybe this is the latest twist on car dealers rolling back odometers :-)

[cfg83]

bandit86 -

Remember that the on-board gauge is typically biased in favor of the car. What jamesqf said is also very important. I have one section of the 210 West where I can get over 70 MPG on my SG, but I know it's because of a long slow decline.

The lesson learned is that if you had asked our opinion before buying the car, we would have been able to warn you. Here is a quick search of the Ecomodder Garage of "Make = Jeep", "Model = Grand Cherokee" :

EcoModder Fleet list - EcoModder.com

Of that list, I think this is the best of the bunch because it has great MPG + a lot of fuel log entries :

Kmachine : 20.38 MPG
Details: Jeep - 2003 Jeep Grand Cherokee Fuel Economy - EcoModder.com

CarloSW2

[cfg83]

Angmaar -

Originally Posted by Angmaar

Instantaneous MPG is different than average.

Very good point. When I am in a steady-state cruise mode I can see fantastic MPG.

CarloSW2

[Frank Lee]

^BTW, that is what the EM performance calculator does- gives the nice steady-state figures. Not knocking it, it's tremendously useful, but don't plug your #s into it and think you'll get the indicated fe over the course of the tank.

[Hubert Farnsworth]

Instantaneous mpg when it is first reset doesn't mean you'd actually achieve said mpg at the end of the specified distance, sure at exactly 70 mph it may display 23-24 mpg if you reset the computer while drafting/ at steady state for a moment, before it calculates enough fuel and distance has gone through to get a more accurate reading, per the epa as referenced earlier the expected highway average is only 20mpg, therefore that would be a better estimate, (and the combined figure better still as that more accurately reflects 55% city and 45% highway cycle)

[cfg83]

Frank -

Originally Posted by Frank Lee

^BTW, that is what the EM performance calculator does- gives the nice steady-state figures. Not knocking it, it's tremendously useful, but don't plug your #s into it and think you'll get the indicated fe over the course of the tank.

Egg-zactly. If you let it get to you, a commute is an MPG yo-yo. The average is the reality.

CarloSW2

[comptiger5000]

In all highway driving at 60mph, if all is well, that generation Grand Cherokee with a 4.0 I6 should get 20 - 24 mpg with no wind and no very steep hills. If it's not, and you can't get 13 - 14 city, something is definitely wrong.

I'd look into making sure wheel bearings are all good, tire pressures are about 2 psi higher up front than in back (if it's full time 4wd), make sure the front O2 sensor (or sensors, some have 1, some 2, depending on year and CA emissions) are good. Make sure the plugs are good and gapped correctly as well. Not a bad idea to change the fuel filter either, as some have reported a clogged one killing both power and mpg on those Jeeps.

From what I've seen with my mom's 99, the onboard mpg gauge (in avg eco mode) is usually within 1mpg of hand-calculated tank average.

[t vago]

As the driver of a 4500+ lb Dodge Dakota quad cab with a 4.7L V8 engine, I can only say this...

You seriously expected to get decent gas mileage out of a Jeep Grand Cherokee? Bwah-hah-hah-hah-hah!!!!!!!

[bandit86]

i still dont quite think any of you understood the original post. the absolute best mpg i got on a test drive I cannot duplicate again, although today being warmer it was getting closer. I can't remember how warm it was when I took it for a test drive.

I never said anything about average numbers not matching, or tank filup not matching the display.

i did not buy the Jeep to get exceptional fuel economy, it's an all around work truck, I needed 4x4 which a civic vagon would not have had.

[jamesqf]

Originally Posted by bandit86

I needed 4x4 which a civic vagon would not have had.

Subaru.