MPG Trip computer vs. my calculation
 

Has anyone else compared the average MPG the trip computer returns on their Elantras? I have a 2008 EX; for example, during my last few fillups, my calculation is always higher than the trip computers. Last time I calculated 29 vs 27 on the trip computer.

This is normal behavior. The trip computer measures vacuum pressure from the intake, while your calculation is true miles vs fuel used. Which one do you think is more accurate?

First, be sure to reset the computer every fillup. Second, make sure you fill up the same way every time. It's very easy to fillup more or less and that will throw off your manual calculation. There have been times my trip computer and manual calculation are off by 1 mpg but for the most part they are within 0.2 mpg.

I hear a wide range of info on this issue. Usually when there's a difference, though, the trip computer has the higher number.

In addition to our Car Reliability Survey, TrueDelta also conducts a real-world gas mileage survey that includes questions on driving style and driving conditions, so people can find the responses that fit the driving they do.

Results for the Elantra here:

Real-world Hyundai Elantra gas mileage

A bit of a core dump right now--working on that. It's possible to report results from a manual calculation, trip computer, or both. Haven't performed an analysis to see how large the differences tend to be, but it's possible and I should. Just need more time...

Hyundai Trip Computer
 

The trip computer in my Santa Fe re-sets the average fuel comsumption file with every fill up. I would like to monitor fuel mileage over a few tank fulls and different driving situations. The manual indicates this average calculation must be reset manually by use of the reset button. Is there some setting I can adjust/correct to prevent the automatic re-set?

There is no automatic reset of the average fuel economy. It must be done manually. And it should be reset at every fillup or the reading will not be accurate.

Mine definately auto resets with every fill up. Did it again this AM. Would it not be usefull to monitor average over several tank fills? Does this computer use litres over kilometers or the gas guage to do calculation?

Hyundai just confirmed auto re-set with every fill up. Uses gas guage to calculate useage.

Interesting. I wasn't aware that any of them auto-reset.