My 2006 Jeep Grand Cherokee has a Gallon/Milage feature that tells you what your eastimated maiage per gallon is.My question is do you reset it while the vehicle is in motion or at a complete stop.My Jeep should get 15/21 and when I reset the guage while in motion it stays around 21-22 highway.Thanks Joe
Gallon/Milage indicator
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Reset at every fill-up.
You can also never reset it and keep it as a running average. Then calculate your tank to tank when you fill up.
Your OBC will probably read a little high.
You can also never reset it and keep it as a running average. Then calculate your tank to tank when you fill up.
Your OBC will probably read a little high.
Is it sort of like a simplified trip computer where you can reset it at any time and it will keep track of your mpg until the next time you reset it?
If so you can use it to figure your mpg for certain trips, for a whole tank of gas, for a day's driving or whatever you want to. Whether you reset it when moving or not is up to you: it will calculate the average from the moment you hit the button.
I think every car should have one because it can tell you all sorts of useful things about when your driving is most and least efficient.
If so you can use it to figure your mpg for certain trips, for a whole tank of gas, for a day's driving or whatever you want to. Whether you reset it when moving or not is up to you: it will calculate the average from the moment you hit the button.
I think every car should have one because it can tell you all sorts of useful things about when your driving is most and least efficient.
I have a similar computer in my car, and I reset it on most trips more than 10 miles. Then I try and keep the average up. It's no fun to only reset it at each fill-up (though I used to do that).
The Driver's Information Center on my Buick has such a feature. It tends to report about 10% high on average fuel economy, and about 10% low on gallons used. But that's pretty consistent, so I can just take 10% off the average fuel economy. This comes out very close to the reading I get by measuring how many gallons pumped to full, divided into the miles.
I zero out the gallons used, average fuel economy, and miles driven counters at each full fillup.
The gas gauge is a much rougher guide.
I zero out the gallons used, average fuel economy, and miles driven counters at each full fillup.
The gas gauge is a much rougher guide.
Reset it whenever you want real-time data. It's useful for seeing how mileage is changing and how your driving is affecting your mileage. It's not useful for actually calculating mileage; they usually read high.
Originally Posted By: Benzadmiral
It tends to report about 10% high on average fuel economy, and about 10% low on gallons used. But that's pretty consistent...
Mine used to report slightly high as well, a few percent. I was surprised to find after having my injectors professionally cleaned and flow-tested that it then started to report with excellent accuracy. It has now drifted to reporting 2-3% high again.
I think it is a good indicator of injector cleanliness and balance.
Incidentally I am running various injector/cc cleaners and tracking the computer's accuracy to see which if any make a difference. So far none have and the past several tanks have all been within that 2-3% high reading.
YMMV on this of course as I'm sure the systems themselves have variances in how they work. However it does make sense that dirty injectors would make it read high as the computer would think that more fuel was being delivered than actually was.
It tends to report about 10% high on average fuel economy, and about 10% low on gallons used. But that's pretty consistent...
Mine used to report slightly high as well, a few percent. I was surprised to find after having my injectors professionally cleaned and flow-tested that it then started to report with excellent accuracy. It has now drifted to reporting 2-3% high again.
I think it is a good indicator of injector cleanliness and balance.
Incidentally I am running various injector/cc cleaners and tracking the computer's accuracy to see which if any make a difference. So far none have and the past several tanks have all been within that 2-3% high reading.
YMMV on this of course as I'm sure the systems themselves have variances in how they work. However it does make sense that dirty injectors would make it read high as the computer would think that more fuel was being delivered than actually was.
True, but the Buick's computer is trying to tell me that *less* gas is being used than actually is! That instead of 11 gallons, I've used only 10, and gotten 24 mpg instead of 22.
I'm going to run some Techron Concentrate through the system before the oil change next month, something I haven't done since I bought the car in August, and we'll see if anything changes.
I'm going to run some Techron Concentrate through the system before the oil change next month, something I haven't done since I bought the car in August, and we'll see if anything changes.
Originally Posted By: Benzadmiral
True, but the Buick's computer is trying to tell me that *less* gas is being used than actually is! That instead of 11 gallons, I've used only 10, and gotten 24 mpg instead of 22.
I think you got this backwards. According to your statement above, the computer is telling you that more gas was consumed (11 gallons), than actually was used (10 gallons).
True, but the Buick's computer is trying to tell me that *less* gas is being used than actually is! That instead of 11 gallons, I've used only 10, and gotten 24 mpg instead of 22.
I think you got this backwards. According to your statement above, the computer is telling you that more gas was consumed (11 gallons), than actually was used (10 gallons).
Originally Posted By: Ray Garlington
Originally Posted By: Benzadmiral
True, but the Buick's computer is trying to tell me that *less* gas is being used than actually is! That instead of 11 gallons, I've used only 10, and gotten 24 mpg instead of 22.
I think you got this backwards. According to your statement above, the computer is telling you that more gas was consumed (11 gallons), than actually was used (10 gallons).
No, Ray, just like that. I drive 240 miles. The computer reports 10 gallons used; the pump, however, clicks off at 11. The computer reports my average fuel economy as 24; computing (240 miles / 11 gal.) yields 21.818181 (I rounded up in my quick example).
I presume GM programmed it this way for those people who only play with the car's gadgets. "Wow! Twenty-four out of a big car like this!"
Originally Posted By: Benzadmiral
True, but the Buick's computer is trying to tell me that *less* gas is being used than actually is! That instead of 11 gallons, I've used only 10, and gotten 24 mpg instead of 22.
I think you got this backwards. According to your statement above, the computer is telling you that more gas was consumed (11 gallons), than actually was used (10 gallons).
No, Ray, just like that. I drive 240 miles. The computer reports 10 gallons used; the pump, however, clicks off at 11. The computer reports my average fuel economy as 24; computing (240 miles / 11 gal.) yields 21.818181 (I rounded up in my quick example).
I presume GM programmed it this way for those people who only play with the car's gadgets. "Wow! Twenty-four out of a big car like this!"
Interesting thread. I've often wondered how the fuel mileage computers built into vehicles work. I'm suspect they don't have a fuel flow device, but use the injector ON time vs. some fuel flow map. Since fuel pressure is regulated this should provide pretty accurate fuel flow. Does anyone know this is indeed the way fuel flow is measured?
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