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Only Hyundai knows....


But it's RPM's, load, speed, acceleration, and I'm sure several other factors. Display's a recent average and takes longer to change the longer your on a tank.
 

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Discussion Starter #4
Only Hyundai knows....


But it's RPM's, load, speed, acceleration, and I'm sure several other factors. Display's a recent average and takes longer to change the longer your on a tank.

That's what I thought also but was hoping one of our resident techs could verify.

In switching from OEM 16" wheels to an odd size 17x7.5 (225x50-17) the MPG went from OEM 34/35mpg to 28/29mpg. Speedo reads 3mph faster than GPS.
I'm going to weigh the two to see the difference in rotating mass.
 

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This might help with the difference in your reading.


https://tiresize.com/calculator/


See what % difference in your tire size and you can just add that back into your reading.
 

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The ECU knows how long each injector is open, how many times they fire, what the flow rate is on them, knows the rpm, miles driven, among other factors. But if your odometer is not accurate neither is your miles per gallon.
 

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Normally like this. Each time you push the reset button it recalculates the average. (I do this for every tank full) If you were to never reset it.. then it will calculate ,from mile one.
Mine resets automatically, when I fill the tank
 

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A better question is the computer's accuracy when calculating MPG.
I've spot checked it against manual calculations and find it's a bit optimistic. But not by much.
Example... the computer would say 39 mpg at fill up but my calculations said 38.5 mpg. Not a huge difference.
And since my car is rated at 36 mpg highway I was winner because it was over the EPA rating.

I have wonder how so many people have a hard time getting decent gas mileage when every car I've owned has always achieved better MPG than what the window sticker says it should get. I drive the speed limit in city streets but often speed on the freeway. My Hyundai seems very happy cruising at 80mph.
 

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Discussion Starter #10
I drive the speed limit in city streets but often speed on the freeway. My Hyundai seems very happy cruising at 80mph.
Same here on both accounts.
But for me there's a fair change in MPG between 70MPH and 80MPH :surprise:
 

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Mystical Korean elves....
 

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It must also keep track in relation to what the tank level is too. Or rather as with mine, when you fill it the number is reset and I assume a table in the ECU is wiped out to start over. But it is much easier to affect the numbers right after filling up than when you are about empty.

If I fill and then go straight out to the highway and set the cruise to 50 I can get over 40 mph pretty fast if I don't stop. But starting or stopping at an intersect then accelerating will eat into that fast. Not so much once down below a 1/4 tank.
 
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