What IS your fuel economy?

[Byteme]

That seemed to be the tipping point though.

Only because it happened about the same time as the rise in diesel vs. gasoline demand. 

Bottom line, as I posted earlier, is it's no single factor. 

[mzziaz]

Diesel is cheaper than gasoline over here, so it's a win-win

[Morris Minor]

EPA  numbers on the 2010 G37 are 19/27.

I get around 21.5 - suburban stop/start traffic. Have never measured highway consumption.