I actually have a question about this... (because I truly want to know more about this).
I understand in the winter you need to use your heater so therefore efficiency goes down, but in the summer I find myself using my AC more and preconditioning the car more before getting in and I'm seeing my efficiency as significantly worse than during the spring/fall. I know not every climate is the same and San Diego is pretty forgiving in terms of temperatures, but having the AC running when it's hot seems like it wouldn't make the the most efficient time, right?
Yeah, my usual experience is that the late spring and early fall are the most efficient times. Still, his point that the winter efficiency will drag the numbers up somewhat is quite valid.
How much remains to be seen - and I'm quite certain that my Ludicrous Raven is doing somewhat better than my prior X75D in the same conditions.