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What Does SULEV Mean? Understanding Low-Emissions Vehicles


Have you seen “SULEV” at the bottom of a vehicle’s window sticker and wondered what exactly that term meant? Or maybe it was a badge on the trunk of a car or hatch of an SUV at a dealership? This acronym actually describes the level of emissions produced by a vehicle in normal operation, and it offers a glimpse into the technologies that are driving the eco-friendly evolution of modern automobiles.

Super Low = Super Good

The term stands for Super Ultra-Low Emissions Vehicle, and it’s a step above ULEV (Ultra-Low Emissions Vehicle). While an ULEV is classified as a car or truck that generates 50 percent fewer tailpipe emissions than the average of equivalent vehicles from that particular model year, a SULEV goes significantly farther by requiring a 90 percent reduction.

The term has been around since the 1990s as part of the EPA’s Clean Air Act, but it took over a decade for the first one to hit the road (the Nissan Sentra). Since then, a number of automobiles, mostly compacts like the Ford Focus and the Hyundai Elantra, have qualified.

What Makes a SULEV?

SULEV vehicleCleaning up tailpipe emissions until they pollute dramatically less than almost every other vehicle requires a combination of factors to all come together. Fuel quality makes a difference. Low-sulfur gasoline is one of the keys to meeting these standards, which means some vehicles will be SULEV in one state but not in another due to different levels of refinement in gas. Engine management and catalytic converter design are also crucial in reducing emissions in these types of automobiles, as a motor must run as efficiently as possible to reduce the level of waste gases that are produced.

How Is SULEV Different From PZEV?

Is there anything beyond the Super Ultra-Low Emissions Vehicle rating for modern cars? Actually, yes, and it’s called a PZEV, or a Partial Zero Emissions Vehicle. A PZEV is a Super Ultra-Low Emissions Vehicle that produces no evaporative emissions at all, which means no gas vapors can escape the tank or fuel system at any time. It doesn’t mean the vehicle has to be electric, although Advanced Technology PZEVs (AT-PZEV) do use hybrid or battery systems. These vehicles are usually built for states like California that have very strict emissions control regulations that require OEMs to produce a certain number of eco-friendly automobiles per model year.

Check out all the fuel & emission system parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on SULEV cars, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Wikimedia Commons.


Benjamin Hunting View All

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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