Porchpkr Posted January 27, 2017 Share Posted January 27, 2017 My 2017 legacy consitently over estimates gas mileage by about 2mpg. Anyone else notice this? Link to comment Share on other sites More sharing options...
upstater Posted January 27, 2017 Share Posted January 27, 2017 My 2017 legacy consitently over estimates gas mileage by about 2mpg. Anyone else notice this? it is the same for every Subaru I have owned. Use Gas Cubby and calculate your MPG average at the pump. Link to comment Share on other sites More sharing options...
MilesA Posted January 27, 2017 Share Posted January 27, 2017 Same here, they tend to be over-optimistic. Values are calculated based on a model in the ECU. Link to comment Share on other sites More sharing options...
whitetiger Posted January 27, 2017 Share Posted January 27, 2017 the computer probably tells you what's possible, and then you go ahead and ruin it with your heavy foot. Link to comment Share on other sites More sharing options...
Porchpkr Posted January 27, 2017 Author Share Posted January 27, 2017 Every tank I reset it. On a full tank of 500 miles or so, it might say I've gotten 32.1 mpg. After filling and doing the math it's always off by a few mpg. Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted January 27, 2017 Share Posted January 27, 2017 I am not sure if it is possible on the 6th gen cars, but on the 5th gen you had a plus or minus 3 rage you could adjust it to and get it pretty close. Link to comment Share on other sites More sharing options...
ammcinnis Posted January 27, 2017 Share Posted January 27, 2017 The topic has been discussed before on this forum. (Search is your friend.) Most people who have done the math report, on average, about a 4% error. If it's important to you, there is a calibration constant that can be adjusted by your dealer (up to +/-10%) to correct for this anomaly. See the Legacy/Outback Factory Service Manual, page MET(diag)-19.MET(diag)-19_User_Customization.pdf "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
hkshooter Posted January 27, 2017 Share Posted January 27, 2017 Discovered this a year ago. I simply subtract two from whatever the car says. It's certainly not worth complaining about. Sent from my SM-G920V using Tapatalk Link to comment Share on other sites More sharing options...
ehsnils Posted January 27, 2017 Share Posted January 27, 2017 Every tank I reset it. On a full tank of 500 miles or so, it might say I've gotten 32.1 mpg. After filling and doing the math it's always off by a few mpg. That's the same with every trip computer - the system don't measure the actual volume used but calculates it from pulse width and frequency to the injectors. Link to comment Share on other sites More sharing options...
ammcinnis Posted January 27, 2017 Share Posted January 27, 2017 ... the system don't measure the actual volume used but calculates it from pulse width and frequency to the injectors. Correct ... and the injectors are nonlinear at short pulse widths, due to inertial and viscous properties of the fuel. My own observation is that the default on-board fuel economy calculation seems to be somewhat more accurate during constant-speed highway cruising than it is for slower in-town driving. "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
Porchpkr Posted January 28, 2017 Author Share Posted January 28, 2017 Thanks for all the information. No, it's not worth complainintabout or dealing with a Subaru dealer. I'm a numbers person. Was just curious of others experiences were with this. Link to comment Share on other sites More sharing options...
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