I think it would be interesting to see a chart of MPG plotted against temperature during the tankful by car. It might give us Midwesterners some insight (no pun intended- I have a Civic) into what we can expect this summer and give the Californians the sense that those EPA numbers would be more accurate if only they left out the other 49 states

 

Expect 10mpg increase in the summer if your in the midwest.

 

So I hear; the chart might be interesting to see!