Here's what temp vs mpg looks like with no AC to skew the hot end of the chart. My 15-year-old AC has finally quit so there's no temptation.
This is the average of all my commutes in the last four years. That should be enough to smooth out any other effects and see a general trend.
The slight dip above 80 is because my morning commute is slightly downhill and more efficient, but morning temperatures never get above the low 80's.
