"PZEV" as used by Subaru in the United States stands for "Partial Zero Emissions Vehicle," a status conveyed on cars, trucks and SUVs that receive an overall rating of 9 out of 10 for their environmental impact. PZEV is the top rating the Environmental Protection Agency confers on gas-powered cars.
As of 2015, Subaru's PZEV vehicle lineup includes the Legacy sedan, the Outback wagon and the Forester SUV. The Impreza compact sedan is also available as a PZEV variant in some markets, and the XV Crosstrek achieves PZEV status in its hybrid trim. The Japanese brand's 2.5-liter "Boxer" horizontally opposed four-cylinder engines use different engine control module programming and catalytic converters to comply with the lower carbon, nitrogen oxide and other emission standards set forth by the EPA that must be met in order to achieve PZEV status. As the law requires, these vehicles also come with an improved warranty for their catalytic converters and other emissions control systems, which in Subaru's case is 15 years or 150,000 miles.
PZEV was developed by the California Air Resources Board, which uses more stringent standards than those federally mandated by the EPA. Developed in response to high pollution in major California cities, CARB standards have been adopted by Oregon, New York, New Jersey, Washington and several other states.
Subaru sells some of its model lineup in both standard and PZEV variants, with the regular 2.5-liter cars having a slightly higher power output. In markets adopting CARB emissions standards, the PZEV variant is usually the only one offered, while in states that only must abide by EPA standards, Subaru tends to sell both side-by-side.