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Understand the Smog Rating

Starting in 2013, all new cars are required to display the updated Federal Fuel Economy and Environment Label (Label). The Federal label provides helpful 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.

Smog Ratings

Every car sold in California is certified by the California Air Resources Board (CARB) and meets a certain emission standard. These emission standards are part of CARB's LEVIII program. Each emission standard corresponds to a Smog Rating, as shown in the table below. Smog Ratings are on a scale of 1 – 10, with 10 being the cleanest.

In 2013 California aligned with the federal emissions standards for cars and light trucks, allowing us to use the smog ratings found on the Federal Fuel Economy and Environment Label.

Model Year 2018

The smog rating chart has been recalibrated in 2018 to reflect new, more stringent Tier 3 emission standards. This is good news, as Tier 3 cars and trucks are much cleaner. This recalibration makes better use of the entire smog rating scale and allows for more useful comparisons between vehicles. Please note: Even though ratings appear to be going down, vehicles are not getting dirtier. A model year 2018 smog rating of 3 is about the same as a model year 2017 smog rating of 6. 

Also, in this new calibration, transitional zero emission vehicles or TZEVs, which are the cleanest plug-in hybrid electric vehicles, previously received a smog rating of 9 but will now be rated based on the standard to which the gas engine is certified.  Therefore, starting in 2018, TZEVs will get a rating of a 7 or 8 depending upon the standards to which they are certified.  For a list of TZEVs, visit our webpage with eligible vehicles for carpool lane stickers.

Given implementation of new federal (EPA Tier 3) and California (CARB LEVIII) emissions standards, older (Tier 2 and LEVII) emissions standards no longer appear on the smog rating chart as of model year 2018.

Smog Rating* EPA Tier 3 CARB LEV III
10 Bin 0 0.000
9 -- --
8 Bin 20 SULEV20
7 Bin 30 SULEV30
6 Bin 50 SULEV50
5 Bin 70 SULEV70
4 -- --
3 Bin 125 SULEV125
2 -- --
1 Bin 160 SULEV160

*Does not include upstream emissions.

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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