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Fuel Economy

Ecomike said:
I started a thread here about 3 months ago and a considerable number of people reported XJ highway mileage as high as 25 mpgs. In fact I bought I bought one that was getting 24 mpg before the head gasket went out. Unless you live in a city with no lights, not stop signs and only downhill trips all the time I suspect the scanner is off, but where is it, the scanner, getting its gasoline volume reading, flow rate data from? The scanner has no flow rate sensor in it, right? So it is estimating that rate or getting a reported estimate from the jeep computer based on injector open time and fuel pump pressure right? Volume does vary considerably with temperature of the fuel!!!!! The computer may be using a default gas temperature assumption.

I would suspect there is an error in there somewhere. The cold air in Canada might be helping the efficiency some. I have seen believable reports as high as 25 mpg highway.
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Not it measures GPH of fuel usage, the problem with it is I have it set with a really high "adjustment factor", so all my numbers are skewed. The unit itself is very capable, but it's just not calibrated.

The cold air in Canada? HAHAHA You do realize there are places in the US that have the same weather I do here don't you? And NO, I don't live in an igloo.

Like I said before, after I goto the gas station and match the number of gallons I add to the tank, to what it thinks I should have added, the calibration will be complete and I'll report back with more realistic numbers.
 
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dlarrivee said:
Not it measures GPH of fuel usage, the problem with it is I have it set with a really high "adjustment factor", so all my numbers are skewed. The unit itself is very capable, but it's just not calibrated.

The cold air in Canada? HAHAHA You do realize there are places in the US that have the same weather I do here don't you? And NO, I don't live in an igloo.

Like I said before, after I goto the gas station and match the number of gallons I add to the tank, to what it thinks I should have added, the calibration will be complete and I'll report back with more realistic numbers.
Click to expand...

what was your mpg before scangauge? how about doing it the old fashion way, convert how many miles you went by looking at the speedo and divide that into how many gallons put in the tank?
 
XJ's squeek/rattle, overheat, and have poor fuel economy. If it doesn't, then it's a counterfeit
tongue.gif
 
Phillips 66 is the only gas in town that doesn't contain ethanol.
Just finished a tank of 66 and there is no doubt that my mileage went up.
I estimate around 3 mpg. Nothing scientific about it, but definitely higher than the E10 garbage.
 
FYI: I bought a scangauge for my '00. The jeep disconnects itself from the scan gauge making it useless for mileage measurements. The manufacture says i might be able to make it work with a vehicle reprogram, but I've not tried.

Anyone get one to work with a 2000?
 
falcon556 said:
Phillips 66 is the only gas in town that doesn't contain ethanol.
Just finished a tank of 66 and there is no doubt that my mileage went up.
I estimate around 3 mpg. Nothing scientific about it, but definitely higher than the E10 garbage.
Click to expand...

Well..... I'd take a 3 MPG gain any day!!!! party1:
 
My lifted XJ with 35's and a 4.7L stroker gets 21 @65 on the interstate @5000ft. Around town if I keep my foot out of it, I get around 17mpg. The key is gearing and getting the engine set up correctly.
 
old_man said:
My lifted XJ with 35's and a 4.7L stroker gets 21 @65 on the interstate @5000ft. Around town if I keep my foot out of it, I get around 17mpg. The key is gearing and getting the engine set up correctly.
Click to expand...

OK, so 5000 ft is a disadvantage, the stroker helps, more displacement and a few less pounds of engine, but what is the diffy gear ratio?
 
law.74 said:
FYI: I bought a scangauge for my '00. The jeep disconnects itself from the scan gauge making it useless for mileage measurements. The manufacture says i might be able to make it work with a vehicle reprogram, but I've not tried.

Anyone get one to work with a 2000?
Click to expand...

Mine doesn't, it's a 2001, it was just mis-calibrated hence the huge lies earlier.
 
I was looking at this awhile back. Does all the other readings work? Like the temp, throttle pos., engine load, ect. I am still thinking of getting it.
 
97XJ Jeeper said:
I was looking at this awhile back. Does all the other readings work? Like the temp, throttle pos., engine load, ect. I am still thinking of getting it.
Click to expand...
The IAT seemed accurate (near ambient at highway speeds maybe 10F higher) and like 150 at idle when it was 50 degrees out, one bad thing about short ram intakes..

The throttle position was pretty accurate except at WOT it seemed like it got lost. Engine load seemed decent, at WOT i figured it woulda went to 100% but i forgot if it went blank or varied around 80 orsomething. The coolant temp was accurate, voltage was accurate, ignition was usuallt 35 in advance. Map was 14.5psi at idle, like 13psi at WOT and 6-8 under most normal accel, 10 under medium accel. Speed and engine speed are very accurate and my mpg seemed accurate as well. Im very happy with mine except that one of the buttons keeps sticking so i sent them an email to maybe get a new one. Only other complaint is it wont remove one of my check engine lights. My mpgs were 18mpg at 75-80mph and 22-23mpg at 60mph with 235's on my 98 with few mods.
 
My scangauge (when its on) seems to be fairly accurate with its gauges, except MPG due to inaccurate settings (due to it turning off with the engine running). I do have one curious thing of note. The TPS reading tends to jump every so often by 10-15 pts. I need to swap out the TPS to see if this happens with a new one. Anyone else see this with their scangaugeII and late model XJ?
 
falcon556 said:
That was before they started mixing ethanol in our gas (E10). I lost approx 4 mpg since then.
Click to expand...
Sorry to necro this thread, but that, right there is the biggest reason why a lot of our Jeep Cherokees, Comanches & Wagoneers lost fuel efficiency & have been getting lousy MPGs...ETHANOL 10%. The stuff increases the chances of gums & varnishes forming on injector nozzles & moving parts, reducing fuel efficiency by ruining proper spray pattern & even reducing proper flow volume, causing the injectors to remain open longer, leakage past the pintle, reduced flow, greater fuel consumption...but this has already been done to death in other forums. The point is, our sources of gasoline have been tainted by E10, excess dirt, moisture, etc., etc. Truly clean, dry, efficient burning gasoline is pretty much a thing of the past.:gonnablow:passgas:
 
http://www.pure-gas.org

Good luck. I've only been to 1 ethanol-free gas station thus far, and it was in AL. The closest one to me in Raleigh is a hell of a drive, and would completely negate the benefit of ethanol-free gas.

EDIT - the nearest one is ~25 miles from my house. 'Tis bullshit.
 
WOW.....
This thread has lasted for quite some time....

The best gas mileage in my 1998 XJ 5 speed was 23-24 mpg was on a trip to the Grand Canyon when the Jeep was new. I have run synthetic lubricants, verify tire pressure, replaced the cap, plug wires, sparkplugs, fuel injectors and clean air filter.
Now with a 5.5" lift 32s and 4.56s I am lucky to get 15 mpg.
 
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