Green Cars You Can't Buy
The only reasonable explanation I can come up with is the fuel blends required by PZEV vehicles is available in sufficient quantity only in California and the others states. If other fuel blends were used the vehicles might not run as cleanly, or even worse than non-PVEZ equivalent vehicles, or maybe even damage the engine. The distribution of boutique fuels is limited to only a few states. It'll take a while, if ever, for the entire US to be using the same type of ultra clean gasoline.