I just updated my web site and charts. I now have 7.5 years of data charting outdoor temperature vs mpg. Web Page Large PDF chart I use the local climate info to calculate the average outdoor temperature during each tank and plot that vs the mpg during that tank.
Thanks for posting this, Paul. With warmer temps just around the corner I have been trying to estimate what my new car may get this summer. Your graph is helpful. I have been checking out data on Ecomodder.com as well. The following graph from Palemalesian is similar to yours.
