I've new to this website. My wife and I are doing research to determine which Hybrid car we will purchase. We love the Lexus GS450 (even though it's gas mileage isn't that great), but we are getting conflicting information on emission information. The car review on this website states "Fewer still boast, as this Lexus does, of being rated a Super Ultra-Low Emissions Vehicle (SULEV) in California, which certifies a car's emissions are 90 percent cleaner than the average new car offered in California in 2004." The review of the Prius states that it's SULEV is 89%, slight worse. The EPA website has a "Green Vehicle Guide" (http://www.epa.gov/greenvehicles) which displays separate scores for pollution and greenhouse gas emissions. The pollution scores are based on the amount of nitrous oxide, carbon monoxide, etc emitted by the vehicle. The greenhouse gas scores is based strictly on carbon dioxide emissions. The detailed description goes on to state that the amount of carbon dioxide is determined by fuel efficiency and fuel type. Based on that the Lexus GS450 gets only a score of 7 of 10, where the Prius is 10 of 10. Also, the pollution score for Lexus is 9 of 10, where the Prius is 9.5 of 10.

So ... how can the Lexus be slightly cleaner (SULEV rating) than the Prius if this EPA information is accurate?