I really disagree with all this. I achieve better than epa ratings with temps in the 90s and 100s. It is important to keep the battery compartment shaded. I got my glass tinted with huper optik. I only get 2 or 3 mpg better performance with more moderate temps. For all the loss of the AC compressor, the performance of the hybrid is also helped in some ways by the higher temps. Park in the shade for a smaller mileage hit due to overheating of the battery and the need to cool it with the auxilliary fan, which pulls AC air across the battery and dumps it outside.