Hi MGBGT,

I may be able to answer some of your questions.

First, California vs US: CA specifies petrol production parameters over and above maximum sulfur content. Since the auto manufacturers have to submit their cars for CARB (local authority) testing, they are probably using CA petrol, and getting results that cannot be generalized to other parts of the country. Same cars, different petrols. That said, I think it is fair to say that if your local petrol has sulfur content as low as that sold in CA, you can use CARB's results, since AFAIK, sulfur is by far and away the major player in determining how effective the post combustion emission control devices are.

Dirty Civic/Clean Civic hybrids:Same engine, but Honda has set some of their production to 'lean burn' air:petrol mixture ratios to improve mpg at the expense of increased emissions. AFAIK, only the cleaner autos are sold in CA; it might be possible to pick up one or the other outside CA, but I am not sure.

Prius II emissions: I'm sure Wayne will post his references. His comment about margins peaked my interest
I posted in the Share section NREL data that is quite detailed on the Prius I. I have read that the Prius II is even cleaner, but that is as close as I have ever gotten to real numbers for the Prius II. NREL uses it's own testing format that is different than EPA or CARB. They did also test the Insight, so you could come up with a fudge factor if you can find the Insight numbers from one of the other agencies. I personally am too lazy, and so use the NREL test that is closest to 50 mpg.

One last point: None of these testing formats include idling AFAIK, so all cars that do not turn off the ICE at stop are getting a free ride, as it were.