This recommended practice provides a standardized test procedure for comparing the in-service fuel consumption of two conditions of a test vehicle or of one test vehicle to another when it is not possible to run the two or more test vehicles simultaneously. An unchanging control vehicle is in tandem with the test vehicle(s) to provide reference fuel consumption data. This procedure is especially suitable for testing components which require substantial time for removal and replacement or modification, such as engines, transmissions, tag-axles, and cab sheet metal. This procedure may also be used for comparison of entire vehicles and for easy-to-change components (those referenced in the Type I test described in SAE Recommended Practice, SAE J1264). The test may utilize fleet vehicles operating over representative routes.
SAE J1321-1986 history
2020SAE J1321-2020 Fuel Consumption Test Procedure - Type II
2012SAE J1321-2012 Fuel Consumption Test Procedure - Type II (Includes Access to Additional Content)
1986SAE J1321-1986 Joint TMC/SAE Fuel Consumption Test Procedure Type II
1986SAE J1321-1981 Joint TMC/SAE Fuel Consumption Test Procedure - Type II, Recommended Practice