How exactly do you determine
How exactly do you determine the range? Is this from the dash mounted "Distance To Empty" readout? Are drivers physically driving the cars to exhaustion? Some other method?
Also, I have a little quibble. Lithium batteries don't lose energy above 25C / 77F degrees. In the LEAF, in particular because it's the only mass market battery EV without thermal management of the battery, the stored energy continues to rise.
RULE OF THUMB
We use 1% increase in stored energy per 4C / 8F above 20C / 70F, and a loss of energy of 1% per 2C / 4F below 20C / 70F. That means that a 20C / 70F battery in a like new condition in the LEAF will have about 21kWh of "usable" stored energy, while at 0C / 32F, it will have 10% less usable stored energy. Conversely, it will have 5% more stored usable energy at 40C / 110F.
What confuses some folks is that temperature controlled cars (other than the LEAF) certainly have reduced range at hotter and colder temperatures merely because the temperature control is consuming energy to keep the battery closer to 20-25C (68F - 77F)
The hotter the battery, the higher it's degradation and service life. The lower temperature batteries have lower energy density but far longer service lives. The intersection of the two lines of degradation referenced to temperature and stored energy also referenced to temperature just happen to intersect around 20C - 25C. That's why temperature controlled cars use this temperature.