Abstract: An engine control unit (400) for a full hybrid engine (100, 101) is provided. The full hybrid engine (100, 101) comprises an internal combustion engine (110) and an electric motor (120). The internal combustion engine (110) is coupled to the drivetrain via a clutch (130). The engine control unit (400) is configured to operate the internal combustion engine (110) in a lean-burn mode, to determine a current load level of the full hybrid engine (100, 101), and to compare the current load level to a lean-burn load threshold (210). The lean-burn load threshold (210) defines a load level below which stable operation of the internal combustion engine (110) in the lean-burn mode is impossible and/or undesirable. If the current load level of the full hybrid engine (100, 101) is below the lean-burn load threshold (210), the internal combustion engine (110) is decoupled from the drivetrain and the full hybrid engine (100, 101) is operated in an electric mode.