Ive been using a ScanGauge II for a few months now and after inputting all the jeeps specs, (engine size, tank size etc), it has totally helped me save gas by giving me a visual and instant read out of my driving habits. Now after "optimizing" my foot work on the gas pedal, Ive found I get about 10mpg city and usually 18-22mpg on the highway. My city mpg seems abnormally low for a 2000 XJ, especially in comparison to how well I seem to do on the highway.

 

Yup. A vacuum gauge does much the same thing but in an old school way.

 

"Yup. A vacuum gauge does much the same thing but in an old school way."

For the price of a scangauge II ($160) you could buy ($160 / 1.39per gal)
115 gallons of gas.

 

True, but the gas saved by seeing an accurate and real time engine read out would allow you to save much more than the initial cost. And if that isnt enough, it also can scan and clear engine codes on the fly. It pays for itself!

 

A vacuum gauge gives you real time data for about $30.

http://www.egauges.com/ProductDetail...fMmhoCvvnw_wcB

 

Yeah that is def cost effective. Id probably do that set up on my 79 Camaro if I ever get it running haha! I do like the digital readout though, having an ODBII has its perks.

 

Getting 14-16 town. Seldom on the open highways, although I know its a lot better.
I installed a fuel/air ratio (narrow band) gauge on my92 when experimenting with HO.
Used a separate O2 sensor downstream of the original.
I found the ECM to be incredibly inconsistent delivering fuel, especially when cruising/coasting.
Accelerating was the only time F/A was below 14:1. Otherwise steady pedal or downhill that AFR gauge was all over the place.

YMMV But the tail pipe and spark plug visuals tell me we need someone to tweek the ECM

 

This.

If you have a stock Cherokee (no big tires, lifts, etc.) and you are getting 14-15 MPG, you have three choices:

1. Fix the way you track your mileage.*
2. Fix your driving habits.
3. Fix your car.

One or more of those three is where your problem lies. There is NO way you should be getting such lousy mileage. Period.



*HINT: If you are doing anything OTHER than actual miles driven (according to a correct odometer) divided by actual fuel used (as tracked by what the pump says when you add fuel), then you are doing it WRONG. If you are doing anything that involves "miles per tank" you don't have any idea what your real fuel economy is.

 

Then something is wrong with your car. Fix it instead of looking for magic.

 

I wonder how it passed emissions testing.

Back to the vacuum gauge. Click on the link below and scroll through the photos showing factory installed vacuum gauges, commonly called Economy gauges. One hose to the intake manifold. One or two wires for illumination at night.

https://www.google.com/search?q=fact...jo6AAw#imgrc=_

So, we should rely on electronics that could be out of calibration, electronically damped, poorly grounded, using sensors that could be inaccurate due to being made in third world countries instead of seeing REAL realtime info from a vacuum gauge?

 

Scangauge, vacuum... I use Ultra-Gauge in my XJ. In my Metro I use a Bluetooth OBD2 adapter and the Torque app.

Pros and cons to all (though I'd say that Ultra-Gauge and Torque have Scangauge beat in almost every conceivable way). Vac gauge is simple and reliable but only yells you one specific thing. OBD2 adapters can be mislead by bad sensors or incorrect calibration by the user, but can display so much other useful information.

Either way is good, and I won't pick on anyone for either way.

 

How exactly are you calculating your mileage?
I use the GasTracker+ app.


What kind/size tires?
Tires are brand new 225x75r15 Firestone Destination LE's

Alignment good?
Alignment is probably 6k old. Could probably use one.

Is your rear sagging?
Rear leaf springs have 200k on them...Pretty saggy, but not terrible.

What is the makeup/condition/age of your exhaust?
Exhaust is brand new from the manifold back. I do have 62mm TB, 703 injectors, CAI, high flow cat, which probably all have some different level of effect on my MPGs.

What is your engine's compression like these days?
I've never done a compression test on the engine because it runs so smoothly, I've never felt the need. I guess I could do one for ****s and giggles.