How accurate is the Fuel Mileage shown on our Trip Computer?

[a48jeep]

This is not a fuel mileage question...but to see what others have made note of regarding the trip computer fuel mileage versus hand, calculated mileage.

I have had my Ecodiesel less than one week and have not filled up since the dealership. I will be checking the mileage myself. My curiosity has me thinking there must be a learning curve as the computer adjusts to my driving habits, daily drive, environment, etc. Further, I suspect once it completes it's learning mode (if ever), there will be many variables which change from tank to tank.

Thanks for your input on this!

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[Josh00333]

Not very. It’s conservative also. At 10 miles I can always add 1-1.5 gal.
/shrug

 

[Free2roam]

Mines usually off and calculated is lower by 1-2 mpg

 

[Trippin01]

Mine is pretty good, when its calibrated to gearing and tire size. Otherwise its off.

That said,.....When it says empty, its usually very thirsty, and can pretty much kill a $100 bill with a frozen gas station burrito thrown in.

 

[jcarbs]

it's not very consistent. There are times it's as much as a mile or two to high and other times as much as a mile to low. Very confounding.

 

[bleda2002]

This is not a fuel mileage question...but to see what others have made note of regarding the trip computer fuel mileage versus hand, calculated mileage.

I have had my Ecodiesel less than one week and have not filled up since the dealership. I will be checking the mileage myself. My curiosity has me thinking there must be a learning curve as the computer adjusts to my driving habits, daily drive, environment, etc. Further, I suspect once it completes it's learning mode (if ever), there will be many variables which change from tank to tank.

Thanks for your input on this!

Its very accurate for the range its measuring, but it is not like a lifetime fuel average so over a whole tank it can be off a small bit, especially if half the tank was city and half highway. It seems to be the last 100-150 miles averaged in my experience.

 

[johnparjr]

I used to track it on mine and was alway pretty accurate so I don’t anymore

 

[ShadowsPapa]

Seeing you are talking MPG on the cluster and NOT "range" or "miles remaining on this tank" -

Mine has been spot-on or at least within .1 or .2 mpg in most cases.
I did not use the speedometer to calibrate, I used the odometer and tweaked until the odo and GPS device agreed to the tenth of a mile over several miles.

Most people find it to be off for one of these reasons, or a combination of them -

They calibrated by speedometer and can still be way off because it's the odometer that counts. Speedometers display in full miles per hour, not fractions. Radar signs can be off a little bit as well. And the amount it's off by is a percentage, not a hard "off by 1 mph".

When you fill the tank you are not always putting in the EXACT same amount or to the EXACT same level each time. What's the temperature of the fuel? Gas expands and contracts quite a bit with temperature changes. Are you parked in the exact same place at the exact same pump?
The amount you put back in can vary by anywhere from a tenth or two to a gallon.

So if your speedometer is off a touch and you got .4 gallons more in, or less in, than last time - your calculations will be off.

I set up my Garmin GPS, used an app on my phone (phone not connected to truck by usb) and I drove from Altoona to home taking the long way home - backroads.
When I got home the odometer/trip meter and GPS and phone all agreed to the tenth of a mile.
I found that over 3 or so tanks, figuring that I'm not always getting in the exact same amount of gas at the same exact temperature, my phone app calculations on my FillUp app pretty well match the truck's cluster mpg. One fill the truck may be .2 high, next time the app says the truck is a bit lower, and other times they've agreed.

There's no learning to it if you refer to the display showing how many MPG you are getting. It doesn't have to learn. It's comparing the distance you have gone with fuel being consumed.

The miles remaining or range left is a totally different thing - longer discussion

 

[Choatecav]

Don't bet the farm on it's accuracy. I've noticed that it does better when most of the miles are interstate or open road miles. When you are doing average driving around town, up and down the hills here in Tennessee, etc. it ain't much punkin'.

I don't think it factors in terrain very well.

 

[ShadowsPapa]

Don't bet the farm on it's accuracy. I've noticed that it does better when most of the miles are interstate or open road miles. When you are doing average driving around town, up and down the hills here in Tennessee, etc. it ain't much punkin'.

I don't think it factors in terrain very well.

Miles per gallon shown has nothing to do with hills or flats. It's calculating the distance you have driven vs. the gasoline consumed.

Sounds like you are talking range - miles left. That's a different animal and adjusts based on current conditions as you drive.

 

[Choatecav]

Miles per gallon shown has nothing to do with hills or flats. It's calculating the distance you have driven vs. the gasoline consumed.

Sounds like you are talking range - miles left. That's a different animal and adjusts based on current conditions as you drive.

Nope, I'm saying that when I measure it out and calculate it manually, it is off by substantially more after town driving vs open road driving.

 

[j.o.y.ride]

Only thing I care about is miles to empty getting below 30.

 

[Trippin01]

Nope, I'm saying that when I measure it out and calculate it manually, it is off by substantially more after town driving vs open road driving.

I have to agree, truck is male, computer is female, and she’s moody as hell. Just sayin. Range calculation is accurate, but one second I’m getting 25mpg’s and the next I’m getting 4-6mpg’s. I try to reset the average every trip, but no bueno on accuracy, even when I fill up, reset, drive, fill up and do the math to check it. I gave up. Fuel gauge is pretty good, as well as the dummy light telling me what I already know.

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