PZEV refers to emissions, not fuel efficiency. Don't confuse PZEVs with vehicles that rate above average for fuel efficiency. PZEV refers to vehicles with advanced emission controls, but that does not equate with improved fuel efficiency. Most PZEVs come in at about average for their class in fuel efficiency. Hybrid or electric vehicles that meet PZEV standards are sometimes classified as AT-PZEV, or Advanced Technology PZEV, because emissions are just as clean, but they get much better fuel efficiency. The standards give automakers eight years for complete compliance.