Quick Guide To Partial Zero Emission Vehicles


Everything you need to know about partial zero emission vehicles

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What are Partial Zero Emission Vehicles (PZEV)?

As the name suggests, Partial Zero Emission Vehicles, or PZEV for short, are automobiles that were specially designed to meet stringent emission standards in the US. They are not necessarily hybrid cars, but they are more environmentally friendly than traditional gas-fed vehicles. Key factors that define this specific classification include:

  • Engine and fuel systems that produce no evaporative emissions
  • Meeting super ultra-low emissions vehicle (SULEV) tailpipe standards
  • Emission control parts are covered by a 15-year/150,000-mile warranty

These cars were originally developed to be sold in California, where air quality standards are stricter, but these same standards have been adopted by several other states, such as Vermont and New York. They serve as a halfway point between cheap, high-emission vehicles and much more expensive full hybrids and electric vehicles. That said, they are not the end-point but rather a step on the journey towards true zero emissions.

If you're wondering "Is my car a PZEV?", you can do a quick online search to see which vehicles in the USA meet SULEV standards. Some examples of the PZEV cars on the list include the:

You'll note this list is mostly older vehicles; the reason for this includes the fact that most automakers chose to focus on hybrid, electric, or advanced technology partial zero emission vehicles (AT-PZEVs), with PZEVs featuring more like a stepping stone in this process.

PZEV vehicle Nissan
Car Air Exhaust Buick
PZEV car like VW Golf Volkswagen
PZEV Motor Settings Subaru
PZEV Engine Control Module Porsche

Special Equipment Required to Meet SULEV Standards

Naturally, what it takes for the engine of a PZEV to meet these regulations varies from vehicle to vehicle, with certain automakers like Subaru taking it a step further with its enhanced engine control modules. Still, while there are quite a few enhancements, the changes are rather minor compared to what you'd find in an MHEV or PHEV. This helps to keep costs down, both for the manufacturer and the buyer.

In order for a traditional gas-powered vehicle to earn the classification of PZEV, the engine and fuel system need to be tweaked in a variety of ways. All PZEV cars need to include the following:

  • Anti-Permeation fuel system liners: These specially designed liners, along with tight fuel injectors, prevent gas from leaking out and saturating the fuel system. This, in turn, reduces off-gassing, evaporation, and gas emissions.
  • Carbon air intake traps: Fuel vapors remain in your car's combustion chamber for some time after you turn off your vehicle. Since these can leak out, special intake filters with charcoal canisters are fitted, which capture and absorb them.
  • Carbon canister scrubbers: Just as vapors can escape from your engine compartment, so too can they get out of the fuel tank via the fuel cap. To meet PZEV emissions standards, a special scrubber insulates the fuel line, preventing these vapors from escaping.
  • Close-coupled catalytic converters: A more closely coupled version of the standard equipment have an extra lining of precious metals that react to nitric oxide and nitrogen dioxide, catalyzing them into less harmful gases
  • Engine control module: Some PZEV vehicles have special control modules that delay ignition timing in winter. This allows the rest of the system parts to warm up before the creation of emissions, meaning that they can absorb them properly.
Car Carbon Air Intake Cobb
Badge PZEV Car Subaru

What are the Benefits of PZEV Technology?

All of these changes to the components work towards lowering the emissions of PZEVs, but there are a few knock-on advantages, too. These comprise:

  • Cleaner emissions without any loss in performance
  • Easier and cheaper to repair than complex hybrids
  • No special fuel or charging stations are required

But this is not to say that they are perfect. Technology has advanced quite a bit since PZEVs were first introduced, proving that they are little more than a stepping stone on the route to true zero emissions. As such, they:

  • Don't provide any additional performance
  • Don't reduce carbon dioxide emissions
  • No money saved from better fuel economy or incentives offered

Nowadays, we have wider access to hybrid vehicles, both mild or plug-in, and even quite a few electric vehicles. With many manufacturers making the move towards full electrification, it is likely that PZEV technology will be applied to the few remaining gasoline-powered vehicles to ensure that they at least try to meet emission regulations when EVs are slamming it out of the ballpark.


What does PZEV stand for?

Partial zero emission vehicle. These are essentially gas-powered vehicles with extra equipment to reduce their harmful gasses output. Toyota has quite a long list of PZEV vehicles, as do Chevrolet, Ford, and Lexus.

Which states have strict emissions rules?

In the US, six states are known as the clean or PZEV states - California, New York, Maine, Oregon, Massachusetts, and Vermont. Aside from these, other states with higher-than-average emissions regulations include Maryland, Rhode Island, Alaska, Washington, Connecticut, New Jersey, and Pennsylvania.

What does the PZEV warranty cover and for how long?

To be deemed a PZEV, a vehicle must have a warranty that covers the fuel system for 15 years or 150,000 miles, as well as the traction battery for 10 years or 100,000 miles.

Do PZEVs qualify for incentives?

Unlike true hybrids or electric motor vehicles, PZEVs do not generally benefit from any incentives, like tax credit awards, aside from their extended warranty periods. However, there are a few exceptions to the rule, and you'll have to check with your local dealerships for more information. With the latest changes to these incentives and tightening regulations around the world, it may still be more logical to skip over the PZEV segment and aim for a hybrid, if you can't afford a fully electric option.

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