What exactly is ‘PZEV’?

Legacy-pzevBy Allen Penticoff
Mr. Green Car

I was recently on a road trip and was passed by a Subaru Forester with a badge on the tailgate that proclaimed it to be “PZEV.” I made a note to myself to look up just what that means. Here is what I found out.

PZEV is Partial Zero Emissions Vehicle. Suburu claims it builds the cleanest gasoline powered cars on the market. The catch to this sort of rating is that there is more to it than just what comes out the tailpipe or having the best fuel economy. Although any vehicle that burns less fuel is always going to be “cleaner” overall than one that burns more fuel – particularly when it comes to carbon dioxide emissions. But it is possible to remove harmful things in ways that don’t involve burning fuel.

One of the leading causes of smog is unburned hydrocarbons – basically raw gasoline fumes. Subaru (as do other manufacturers) have designed fuel systems that do not vent gasoline fumes to the atmosphere and limit this from happening when refueling. Subaru has a crankcase carbon filter that absorbs unburned hydrocarbons when the engine is shut down. They also make their fuel injectors close completely when shut down so as to not leak at all.

To get a PZEV rating, the vehicle must reach the EPA’s Super Ultra Low Vehicle Emissions Standard (SULV). To achieve this, Subaru uses an upgraded catalytic converter that has a finer mesh with more precious metals (a catalytic converter’s basic job is to “burn” unburned hydrocarbons before they exit the tailpipe, however few reach 100 percent efficiency at doing this). The engine computer is programmed to run the exhaust hotter on startup to heat up the catalytic converter faster and speed its reduction of emissions. And overall the engine computer (ECM) follows a program to reduce emissions wherever possible. Another requirement of the PZEV designation is that the emissions components have a 15-year, 150,000 mile warranty. All this has helped increase the fuel economy some with no sacrifice in performance according to users of the Subaru Forester Owner’s Forum.

Subaru has done much more than just make efficient all-wheel drive vehicles. Since 2004 their factories have had zero landfill waste. What cannot be recycled is burned to produce electricity. They have also partnered with six organizations that promote environmental stewardship; those are: the National Park Foundation, Leave No Trace, International Mountain Bicycling Association, American Canoe Association, United By Blue, and the Greensgrow Philadelphia Project. As anyone who has observed on the road or in their advertising, Subaru appeals to those who enjoy outdoor recreation – and their cars are often plastered with environmental bumper stickers. These owners also tend to hang onto their beloved Subarus for a very long time (and thus a lower environmental impact of a replacement vehicle).

We often think that “smog” is a problem only in Southern California. Well folks, it is right here in Rockford. On a windless day, a dome of yellow-brown air builds over the city (I can see it from my house) and the air literally stinks of it. This is true of every city. On windy days it just blows somewhere else. On many occasions I’ve been flying between Rockford and Minneapolis and observed their pollution heading our way. And as much as California has done to reduce emissions and is a leader in regulating vehicles for lower emissions – they are now the recipients of China’s vast air pollution problem. So buying a PZEV is important for the environment. The more of them that are bought, the more the market will respond to the demand. Demand it.

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