A method for controlling an engine assembly and an engine assembly, said engine assembly comprising: an engine configured to convert energy in a fuel into primary output energy and secondary output energy wherein the primary output energy consists solely of primary output kinetic energy in the form of a rotating crankshaft for onward transmission to a gearbox and/or a load and the secondary output energy comprises secondary output kinetic energy and secondary output thermal energy. The assembly further includes a recovery device configured to convert the secondary output energy to potential energy; a transducer suitable for converting the potential energy to tertiary energy for conversion either directly or by the engine into primary output energy; and a controller configured to implement an equivalent consumption minimization strategy in order to control overall consumption of fuel by continuously optimising a proportion of the primary output energy derived from the energy in the fuel and a proportion of the primary output energy derived from the tertiary energy.