Internal combustion engine control device

An internal combustion engine control device comprising an engine control unit, the engine control unit configured to:

• estimate a fuel temperature of fuel supplied to a combustion chamber;
• acquire a fuel pressure at which a fuel injection device injects the fuel;
• detect that the fuel injection device is closed when the fuel temperature reaches a designated temperature and calculate a valve closing time of the fuel injection device;
• calculate a valve closing delay time taken from start of valve closing to completion of the valve closing by the fuel injection device in a valve opening state for each of the plurality of designated temperatures based on a plurality of valve closing times calculated at a plurality of different designated temperatures, normalize the plurality of valve closing delay times calculated for each of the plurality of designated temperatures with the fuel pressure, and calculate a difference between the valve closing delay times;
• calculate a synthetic fuel content rate of the fuel stored in a fuel storage unit based on characteristic data indicating a relationship between the difference between the valve closing delay times and the synthetic fuel content rate of the synthetic fuel contained in the fuel;
• and
• control an internal combustion engine such that an exhaust temperature of an exhaust gas discharged from the combustion chamber becomes not less than a threshold temperature based on the synthetic fuel content rate.