How accurate is it?
Senior User
Joined: Dec 2003
Posts: 172
Likes: 0
how accurate is even hand calculating? what if the tank isn't all the way full? what if your odometer is inaccurate?
I find that most stock vehicles speedometer read slightly (about 3%) faster than you are really going. Great when avoiding tickets but not so great when figuring mileage. I figure if the speed is off than the distance is off as well. And if you want to think about it a little further it also means you get shorted on some of your warranty...
And even if your speedo is spot on at purchase it will become more inaccurate as your tires wear. It will read slightly faster (and the odometer further) than you are really going because your tires are smaller.
As for the computer, I find that on a stock vehicle the mpg calculations over an entire tank are pretty darn close to hand figures. As far as the dte - this changes constantly based on how you are driving. The computer bases it on a small, current sample of how you are driving. So if you coast or drive easy the dte will increase and if you floor it for a ways it will drop dramatically. It's not perfect.
Best rule of thumb is to fill up when your fuel guage reads low.
Just my 2¢
I find that most stock vehicles speedometer read slightly (about 3%) faster than you are really going. Great when avoiding tickets but not so great when figuring mileage. I figure if the speed is off than the distance is off as well. And if you want to think about it a little further it also means you get shorted on some of your warranty...
And even if your speedo is spot on at purchase it will become more inaccurate as your tires wear. It will read slightly faster (and the odometer further) than you are really going because your tires are smaller.
As for the computer, I find that on a stock vehicle the mpg calculations over an entire tank are pretty darn close to hand figures. As far as the dte - this changes constantly based on how you are driving. The computer bases it on a small, current sample of how you are driving. So if you coast or drive easy the dte will increase and if you floor it for a ways it will drop dramatically. It's not perfect.
Best rule of thumb is to fill up when your fuel guage reads low.
Just my 2¢
Mountain Pass
Joined: Jul 2006
Posts: 111
Likes: 0
From: Upstate, NY
My owners manual says:
Therefore it is perfectly understandable that DTE will not be accurate for each tank full.
DTE is calculated using a running average fuel economy, which is based
on your recent driving history of 500 miles (800 km). This value is not
the same as the average fuel economy display. The running average fuel
economy is reinitialized to a factory default value if the battery is
disconnected.
on your recent driving history of 500 miles (800 km). This value is not
the same as the average fuel economy display. The running average fuel
economy is reinitialized to a factory default value if the battery is
disconnected.
Therefore it is perfectly understandable that DTE will not be accurate for each tank full.
Elder User
Joined: Sep 2004
Posts: 750
Likes: 0
From: Weimar,TX
My over head read out is usually about 1/2 mpg higher than actual hand calc.
When I fill up, I go until the first time it shuts off and I stop there.
Then I do the same next time, and this gives me an accurate number
of gallons to work with. I have been averaging around 17 mpg most fill-ups.
When I fill up, I go until the first time it shuts off and I stop there.
Then I do the same next time, and this gives me an accurate number
of gallons to work with. I have been averaging around 17 mpg most fill-ups.
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