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I am using an OBD-II sensor and the Andriod Torque app to look at my fuel economy and see that it shows a whopping 37 MPG for my Mazda 6, 2005 (2.3 Automatic). This seems fishy as some random googling shows the US Gov rates it at less at around 23.

Anyone else had some experience with the torque app? can you confirm that its in accurate? Also where does the inaccuracy lie, the ECU or the App?

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Have you double checked the MPG yourself? Check out steps 1-6 – Tim May 10 '12 at 16:41
I use an app called "Road Trip" (iOS) that allows me to enter all the data at every fill. It shows me that my mileage is 22 mpg in my Tacoma, where my OBD-II is telling me that I'm getting < 20. – Chase Florell May 10 '12 at 22:00

4 Answers 4

up vote 3 down vote accepted

I can't speak to the Torque app, but in my experience the US Gov ratings are typically quite a bit lower than what you can expect to get in actual normal driving (Gov ratings seem to be based around someone that does 15mph+ over the speed limit all the time, launches from every stop light, does full-throttle passing, and doesn't see red lights until they have to stand on the brakes to make them). So, it's not entirely impossible, but you're getting even better indicated than I would expect given that. Definitely time to compare with actual measurements.

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The EPA lists their specific test procedures: The whole point of this sort of experiment is to gather representative data. There is a "high speed" test procedure now that captures some of the spastic nature that you describe but it isn't quite that silly. – Bob Cross May 11 '12 at 15:28

i am using an OBD-II sensor and the Andriod Torque too. it shows me 22 trip mpg on 4.8 chevy express cargo van. I don't think it's real. this number stays the same no matter how I drive - highways or stop-n-go city traffic.

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Just measure your actual MPG by filling your tank all the way, then divide how many miles you drive until the next fill up by the number of gallons of said fill up.

My mileage was off with a similar setup because I had larger aftermarket rims and tires, which means the car travels a longer distance for each rotation. Even a different profile tire can make a difference, although your discrepancy seems quite large. If you do have a different tire diameter, you should be able to adjust this in the app.

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This is an old question, but as someone already gave an answer yesterday, here I go...

My car doesn't have a milage display, and it also doesn't communicate any information about its current fuel consumption via OBD. (I also don't know if this is foreseen in the generic part of OBD in general.)

It seems, the app "Torque" takes the RPM, the intake air temperature, intake air pressure (all available via OBD) and the displacement (entered by the user) to calculate the air flow through the motor. Assuming a perfect air/gas mixture, the amount of fuel that could be burned is derived, and with the speed via OBD/GPS, the current milage is calculated.

However, this milage is not always correct. Driving downhill, the current consumption should be zero due to fuel cut-off, but the app shows a significant number. Pressing the clutch, fuel has to be burnt to keep the motor running, which leads to a very low consumption. Instead, the consumption shown by the app decreases.

This leads to the conclusion that the app doesn't know anything about fuel cut-off. It just knows how much air is going through the motor and thinks the consumption must be higher at the higher RPM.

Another scenario one can imagine is that the app doesn't display the higher consumption shortly after starting a cold engine.

I don't have experience with this app together with other cars, but it seems it uses the most suitable sensor data. And when it's not available, it tries to derive this data from other sensor data. But this could lead to incorrect results. (Yet, the app does its best to display the milage)

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