Battery disconnected, better gas milage afterwards?

[Ximian]

I had my battery disconnected a month or so ago to install the AIM Solo 2 DL PnP harness. Once I reconnected the battery, I've seen better gas mileage for the last 2 fill ups. I daily drive my car to work in the same traffic conditions, speeds, and temperatures so nothing drastically changed in the environment that would explain the improvement.

My average is 19.2 mpg but currently I'm getting 20.8 mpg. I normally fill up at about 240 miles on the tank, well after the 12.5 liter warning comes up. For the last month, I've been getting the fuel reserve/12.5 liter warning at about 245 miles. As I have more miles driven when the fuel reserve warning comes up, it's not just some calculation discrepancy on the fuel efficiency with a reset due to the battery disconnect.

The car doesn't run smoother or more powerful in a noticeable way.

I did a bit of searching and found someone reporting a similar thing on the E46 saying this could be related to some calibration or adaption from the O2 sensors being wiped. Any ideas on what it could in this case?

[CHE///MIST3]

I concur! ...and would like to know also. While I don't drive my car daily, when I do it's 100-150 highway miles in a daily stretch...at that distance I can tell that my dash-indicated mileage went from about 17.5 mpg to about 19.0 after doing a battery disconnect/re-connect.

GM

[wfdeacon88]

Same after a tune, from what I remember.. part of the tune is clearing adaptations also.

[sdbmwcoding]

Disconnecting the battery resets certain adaptations, I'm not entirely sure which ones exactly as there's like 10-15 but mpg improvements could be an effect to that.

[pbonsalb]

Reset your mpg meter by holding the stalk down and you will get the same effect if you are highway or secondary road driving. Over time, it should average itself back to what it used to be. Try zeroing it out when in a highway trip so you can see your highway mpg before it gets averaged in with your stop and go city driving.