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My first post.

The Prius has emissions of polllutants of about 104 grams / Km ("a 55% reduction over conventional engines")according to a recent Car and Driver review. I would like to know where I can find this information for other vehicles, gas and hybrid. I have googled and looked in .gov websites, but no luck. Does any one know where I can find this information for different vehicles?

If known, I think the number would also have to be adjusted for actual mileage. My 4 cylinder Tacoma pickup has an EPA rating of 26 MPG, but I just scored 32 MPG on a recent trip. Therefore, it seems to make sense that I would multiply the grams/km by a factor of 26/32, assuming a linear relationship....

Actual numbers make more sense to me than LEV-ULEV classifications.

Some emissions information, by model, is available from a CARB (http://www.arb.ca.gov/msprog/onroad/cert/cert.php#6) site. Don't know if it has the same form that you are looking for.

This was posted somewhere today, but don't remember if it was cleanmpg or priuschat.

That looks like a measurement of CO2, which does scale directly with fuel usage.

CO2 is a global-scale pollutant which causes climate change. I think the LEV/ULEV classifications are based on "conventional" pollutants like nitrogen oxides and unburned hydrocarbons that affect local air quality, but I'm not sure.

If known, I think the number would also have to be adjusted for actual mileage. My 4 cylinder Tacoma pickup has an EPA rating of 26 MPG, but I just scored 32 MPG on a recent trip. Therefore, it seems to make sense that I would multiply the grams/km by a factor of 26/32, assuming a linear relationship....

Actual numbers make more sense to me than LEV-ULEV classifications.
I suspect you are correct. My understanding is that the raw pollutant data is concentrations (ppm = parts per million) in the exhaust gas stream. These would be multiplied by the total air volume in (or perhaps the exhaust flow out) during the test cycle to yield a mass (grams) of each pollutant gas. And finally divided by the "distance" the vehicle went during the test cycle.

I looked on the EPA site for info on the actual procedure but was unable to find it.

But in any case it seems to me that the emissions figures would be valid only for the particular conditions of the test, not for the myriad of conditions on the road, not to mention driving strategies. For example, if I FAS and coast there are zero emissions during the FAS, which would reduce the actual emissions over that stretch of road versus just driving along in gear.

I believe that the CO2 emissions would scale rather directly with mpg. The "C" in CO2 emissions comes almost completely from the carbon in the gas which is burned. And most of the "C" in gas will end up as CO2. I believe only a small proportion will come out as CO or unburnt hydrocarbons.

Our local paper has an auto review that always features the "Carbon Footprint" statistic. It is referred to as "annual carbon emissions in kilograms". Today's paper for example reviews the Mazda 3 Sport and the number is 3552.

That number it leaves me totally in the dark. I wish they would put in some sort of explanation: what's a good/bad number, what's the norm, what sort of test was involved, etc.

I know that British and European governments track these sorts of statistics, and CO2 emissions are one of those things that car manufacturers list along with fuel economy figures. Here's a British VW website with info on the Jetta (it includes the 2.0 Turbo and 2.0 TDI common in the USA, but not the 2.5 5-cyl.)

http://www.volkswagen.co.uk/#/new/jetta/which-model/engines/emissions/

Can't guarantee it'll be an exact match, as sometimes American emissions requirements differ (USA is usually more stringent vis-a-vis particulate emissions,) and there are often different engines available in European cars, but it might give you a ballpark idea.

EDIT: [slaps forehead] I think fueleconomy.gov has this info. See, e.g.: http://www.fueleconomy.gov/feg/2008car1tablef.jsp?column=1&id=26013