New Battery and new (better)MPG!

[JBMorris]

Hi Folks,
This AM my battery went dead while dropping off the princess's 930 for a new muffler.
A quick-charge unit got it started-with difficulty- and the ABS and brake warning lights lit, but went off and back on for the short drive home.
While the old (+-) 4 yrs. was out, joined the two leads together for 15 seconds, then put in a new battery.
On an 18 mile trip, noticed the dash MPG calculator went up to 24.9 mpg, whereas the best previous max was 18.5.
This is hard to believe as the last time the battery was disconnected was to replace my ETM with a XEMODEX unit and it took quite some time to read out 18.5.
Also, the ABS and brake light warnings stayed off. . .
Good luck or a coincidence?
Appreciate your thoughts!

[BillAileo]

My guess is coincidence. I believe once your car is started a properly functioning alternator would compensate for any variations in battery charge. Probably the result of road circumstances & weather. Besides, 18 miles is a pretty short test sample.

[JRL]

Of course you could just reset the mileage readout in 3 seconds without disconnecting the battery and going thru all that

[h20ham]

how influenced is load draw, if the battery will not take a charge the alt works harder. like an air conditioner

[JRL]

They ALWAYS run better after a battery disconnect (ECU reset) but it will go back to where it was in a day or ao