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Understand the Smog Rating

In California all vehicles manufactured after January 1, 2009 were required to display a Greenhouse Gas Rating and Smog Rating as part of the California Environmental Performance (EP) Label. These ratings are important because it gives car buyers the ability to determine quickly how much a vehicle pollutes compared to all other vehicles on the market.

New Fuel Economy and Environment Label

In 2012 California harmonized its consumer vehicle labeling program with the Federal program so that starting in 2013, all new cars are required to display the new Fuel Economy and Environment Label (Label). The Federal label has a similar ranking system as well as additional ways to compare vehicles, such as:

  • New ways to compare energy use and cost between new-technology cars that use electricity and conventional cars that are gasoline-powered.
  • Useful estimates on how much consumers will save or spend on fuel over the next five years compared to the average new vehicle.
  • Easy-to-read ratings of how a model compares to all others for smog emissions and emissions of pollution that contribute to climate change.
  • An estimate of how much fuel or electricity it takes to drive 100 miles.
  • Information on the driving range and charging time of a plug-in vehicle.
  • A QR Code that will allow users of smartphones to access online information about how various models compare on fuel economy and other environmental and energy factors.


Smog is a haze-like form of air pollution produced by the photochemical reaction of sunlight with volatile organic compounds, including Non-Methane Organic Gases (NMOG) and Oxides of Nitrogen (NOx), that have been released into the atmosphere, especially by automobile operation.

EP Label Smog Rating

Smog Ratings are on a scale of 1 – 10, with 10 being the cleanest. The average vehicle available in California today has a Smog Rating of 5. The table below shows the different pollutant levels associated with each Smog Rating, and how those levels relate to Federal and California certification standards.

How the EP Label Smog Rating is Determined

Every car sold in California is certified by the Air Resources Board (ARB) and meets a certain emission standard. These emission standards are part of ARB's Low Emisson Vehicle program. Below is a table that provides the emission standards and the grams per mile of pollution associated with each standard. This is then associated with a certain Smog Rating. The grams per mile of NMOG and NOx are the amounts of smog forming pollutants that come from the car’s tailpipe, and that evaporate from the car.

Smog Rating* Emission Standard NMOG + NOx (g/mile)
10 ZEV, Bin 1 0.000
9** ATPZEV, PZEV 0.030
8 SULEV, LEV2 SULEV, Bin 2 0.030
7 Bin 3 0.085
6 Bin 4 0.110
5 LEV 2 ULEV 0.125
4 LEV 2 LEV, Bin 5 0.160
3 Bin 6 , SULEV (Medium Duty Vehicle) 0.190 - 0.200
2 Bin 7 0.240
1 Bin 8, LEV 2 ULEV (MDV), LEV 1 ULEV 0.325 - 0.356

*Does not include upstream emissions.

**A Smog Rating of 9 was given to vehicles certifying to the California PZEV and ATPZEV standards based on the longer useful life, zero evaporative emissions requirements, and extended warranty for these vehicles compared to vehicles certifying to the SULEV standards.

Additional Resources

Find Clean Vehicles

Slide arrows to view vehicles by rating. Rating of seven or higher are the cleanest.

Greenhouse Gas

Smog Rating

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