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Vehicle and Engine Certification

Information about Family Naming Conventions for Vehicles and Engines

On this page:


A family is the basic unit that EPA uses to identify a group of vehicles or engines for certification and compliance purposes.

EPA uses many terms for "family", including:
  • Engine family;
  • Test group;
  • Vehicle family;
  • Durability group; and
  • Evaporative and/or permeation and/or refueling family.

A manufacturer should apply for new certificates and pay the appropriate certification fees for each family name that it intends to produce for sale in the United States.

A family name is a 12 character code that identifies all parts of that particular engine.

The typical naming convention is shown below, although some sectors have a slight variation.

The first character is model year code, 2-4 are manufacturer code, 5 is industry sector code, 6-9 is engine displace code or family type descriptor code, and 10-12 is manufacturer's self-designated code.


For dual or variable displacement families, enter the maximum displacement. If the displacement is given in liters, the decimal point count as a digit. In all cases, the displacement will be read in liters if a decimal point is included and it will be read in cubic inches or cubic centimeters if there is no decimal point.

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Follow these steps to create your family name:

STEP 1: Find the applicable model year code.

From the table below, find the code for Position 1 of your family name.

Code Model Year
1 2001
2 2002
3 2003
4 2004
5 2005
6 2006
7 2007
8 2008
9 2009
A 2010
Code Model Year
B 2011
C 2012
D 2013
E 2014
F 2015
G 2016
H 2017
J 2018
K 2019
L 2020
Code Model Year
M 2021
N 2022
P 2023
R 2024
S 2025
T 2026
V 2027
W 2028
X 2029
Y 2030
Code Model Year
1 2031
2 2032
3 2033
4 2034
5 2035
6 2036
7 2037
8 2038
9 2039

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STEP 2: Determine your manufacturer code.

This code is the 3-character, alpha-numeric code that EPA assigns to each company. Use this code for Positions 2-4 of your family name.

For more information about registering for a manufacturer code, see: 

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For help on using the table:

STEP 3: Find your industry sector.

Click on your industry sector to view specific instructions for determining Positions 5-12 of your family name.

Industry Sector Industry Sector
California-Only Medium-Duty Vehicles A
Large Nonroad Spark-Ignition Engines
(>19 kiloWatts)
Highway Motorcycles C
Complete Heavy-Duty Highway Vehicles
(8,500 to 14,000 pounds GVWR; tested on chassis dynamometer)
Heavy-Duty Highway Gasoline (otto-cycle/spark ignition) Engines
(>8500 pounds GVWR)
Heavy-Duty Evaporative Families F
Locomotives (freshly manufactured) G
Heavy-Duty Highway Diesel (compression ignition) Engines
(>8,500 pounds  GVWR)
Light-Duty Vehicles and Light-Duty Trucks/Medium-Duty Passenger Vehicles J
Locomotives (remanufacture system) K
Nonroad Compression-Ignition Engines L
Marine Spark-Ignition Engines M
Marine Compression-Ignition Engines (including IMO) N
Permeation Families P
Light-Duty Evaporative/Refueling Families R
Small Nonroad Spark-Ignition Engines
(<19 kiloWatts)
Light-Duty Trucks/Medium-Duty Passenger Vehicles T
Light-Duty Vehicles V
Off-Highway Motorcycles/All-Terrain Vehicles/Utility Vehicles X
Snowmobiles Y
Heavy-Duty Highway Tractors and Vocational Vehicles * 2
Heavy-Duty Highway Trailers 3
Heavy-Duty Highway Powertrain Family 5
Light-Duty Durability Group Various options based on
Combustion Cycle

* This also includes heavy-duty highway vehicles at or below 14,000 pounds GVWR that are not tested on a chassis-dynamometer for certification under 40 CFR Part 1037 (i.e., certified to the requirements and standards of §1037.105, per §1037.104(f)) and powertrain testing configurations as described in 1037.231 (encompassing engine, transmission, and axle) when powertrain testing is used for certification of any vehicles within a family.

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