Engine Family Number

What is an engine family number?
An engine family number is a number given to a specific engine used by a manufacturer. Auto manufacturers might use the same engine in many different vehicle models, or they may use several different engines within the same vehicle model. The engine family number identifies which engine is used, and it is important because a vehicle’s emissions are certified by engine family. So, two seemingly identical vehicles may have very different pollutant levels because their engines may be different.

Typically, vehicles sold in California and states that have adopted California’s emissions regulations will have cleaner engines (identified by their engine family number) than those sold in other states. A vehicle’s engine family number (sometimes called a “test group”) can be found under the hood of the vehicle on the Vehicle Emissions Control Information Label.

How is an engine family number search useful?
Search for a used vehicle with the cleanest smog score – If you are considering buying a used vehicle that you think might have a clean smog score, you can double check by looking up the engine family number. Just look under the hood of the vehicle and write down the engine family number, or test group number, and type it in on the search page. You will know right away what the smog score is of that particular vehicle, and you will also be shown any other versions of that vehicle that might have a different engine – and a different smog score.

Determine the environmental impact of the vehicle you are driving – If you are wondering what the smog score is of the vehicle you are currently driving, you can find out by searching by engine family number. Just look under the hood of your vehicle on the Vehicle Emissions Control Information Label and write down the engine family number, or test group number, and type it in on the search page.


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