The designation “Partial Zero Emissions Vehicle” (PZEV) has many people perplexed. Certainly, childhood math would tell us there is no such thing as “partial-zero.” But while most of us are scratching our heads, PZEVs are quickly becoming the norm in gasoline vehicles. In fact, under the EPA’s Tier 3 Vehicle Emissions standards passed in 2014, by 2025 all cars sold in America will be PZEVs. But what does this strange designation mean?
The California Air Resources Board (CARB) introduced the term in 1998 as part of an evolving state-wide effort to reduce vehicle emissions and push the commercialization of zero emissions vehicle technologies forward. Partial Zero Emissions Vehicle (PZEV) is defined as an “automobile that has zero evaporative emissions from its fuel system, has a 15-year (or at least 150,000-mile) warranty on its emission-control components, and meets Super Ultra Low Emissions Vehicle (SULEV) tailpipe-emission standards.” In simpler terms, PZEVs are “extremely clean conventional vehicles.”
According to Popular Mechanics, PZEVs possess four unique features that differentiate them from standard combustion engines:
1. Anti-Permeation Fuel Systems Liners: Prevent off-gassing of fuel when vehicles are sitting unused.
2. Carbon Canister Scrubbers: Installed in the fuel-filling line from gas cap to gas tank to trap fuel vapors and destroy them in the combustion chamber.
3. Air Intake Traps: Engine-level filters that similarly capture and destroy harmful fuel vapors that evaporate after a vehicle is turned off.
4. Close-Coupled Catalytic Converters: Bring vehicle engines up to speed more quickly, and remove nitric oxide and nitrogen dioxide during operation.
Amazingly, these relatively minor adjustments to the engine and fuel system result in a 90% or more reduction in localized smog- and acid rain-producing emissions compared to a standard combustion vehicle. Together, they capture hydrocarbons, nitric oxide, nitrogen dioxide, carbon monoxide, and nonmethane organic gases that off-gas in a non-PZEV vehicle. These benefits contribute to cleaner air, but unfortunately, this technology does not reduce harmful CO2 emissions or have any effect on fuel efficiency.
So, while they are an important step in the right direction, ZPEVs were intended by CARB to serve as an interim solution as auto manufacturers worked toward technologically and financially viable zero-emissions vehicle solutions. Hybrid-electric PZEVs (designated as AT PZEVs — Advanced Technology Partial Zero Emission Vehicles) represent the next step, followed by plug-in hybrids and other advanced technologies (designated as Enhanced AT PZEVs), and finally all-electric and other 100% alternative fuel vehicles such as hydrogen fuel cell vehicles (designated as ZEVs, true Zero Emissions Vehicles), which represent the ultimate emissions reduction goal.
Subaru was among the earliest adopters and proponents of PZEV technology, but nearly all of the major brands now offer PZEV models including Mazda, Volkswagen, Honda and Ford. For a complete list of vehicles with ZEV, Enhanced AT PZEV, AT PZEV and PZEV ratings take a look at CARB’s Drive Clean Buying Guide.
As the nation’s vehicle emissions standards continue to increase, consumers can expect to see an increasing number of affordable options in the ZEV family, including PZEVs. As with other innovations in the light-duty vehicle space, including self-driving vehicles, innovation in ZEVs is occurring at a rapid pace. It is not yet clear how each of these innovations will fit together. But one thing is certain: The gasoline cars of today, will not be the cars of the future.
