An engine comprising: a plurality of cylinders (6a, 6b, 6c, 6d, 6e, 6f); a fuel injection device which injects fuel to each of the cylinders; an engine cooling water temperature sensor for detecting an engine cooling water temperature, an engine lubricating oil temperature sensor for detecting an lubrication oil temperature; and a control means being able to calculate fuel injection amount, and being able to start the engine with normal operation in which the fuel injection device injects the fuel to all the cylinders or reduced-cylinder operation in which the fuel injection device injects the fuel to only specific cylinders; and wherein the control means starts the engine in the normal operation, when the engine cooling water temperature is in a very-low temperature range at the time of starting; characterized in that the control means is able to calculate a normal fuel injection amount (Q_NORM) for the case of normal operation, a reduced-cylinder assumed fuel injection amount (Q_RCL) for the case of the reduced-cylinder operation based on the normal fuel injection amount (Q_NORM), and a maximum fuel injection amount (Q_FULL) of the normal fuel injection amount (Q_NORM); and wherein at the time of starting the engine,the control means performs the reduced-cylinder operation when the engine cooling water temperature is larger than a predetermined temperature (TW-TH), and when the engine lubrication oil temperature is larger than a predetermined temperature (TL-TH), and when the fuel injection amount (Q-NORM) at the normal operation becomes smaller than a predetermined amount (Q-TH) in the normal operation, and when the reduced-cylinder assumed fuel injection amount Q-RCL is smaller than the maximum fuel injection amount Q-FULL, and wherein the control means performs the normal operation when at least one of said conditions is not satisfied. a plurality of cylinders (6a, 6b, 6c, 6d, 6e, 6f); a fuel injection device which injects fuel to each of the cylinders; an engine cooling water temperature sensor for detecting an engine cooling water temperature, an engine lubricating oil temperature sensor for detecting an lubrication oil temperature; and a control means being able to calculate fuel injection amount, and being able to start the engine with normal operation in which the fuel injection device injects the fuel to all the cylinders or reduced-cylinder operation in which the fuel injection device injects the fuel to only specific cylinders; and wherein the control means starts the engine in the normal operation, when the engine cooling water temperature is in a very-low temperature range at the time of starting; characterized in that the control means is able to calculate a normal fuel injection amount (Q_NORM) for the case of normal operation, a reduced-cylinder assumed fuel injection amount (Q_RCL) for the case of the reduced-cylinder operation based on the normal fuel injection amount (Q_NORM), and a maximum fuel injection amount (Q_FULL) of the normal fuel injection amount (Q_NORM); and wherein at the time of starting the engine,the control means performs the reduced-cylinder operation when the engine cooling water temperature is larger than a predetermined temperature (TW-TH), and when the engine lubrication oil temperature is larger than a predetermined temperature (TL-TH), and when the fuel injection amount (Q-NORM) at the normal operation becomes smaller than a predetermined amount (Q-TH) in the normal operation, and when the reduced-cylinder assumed fuel injection amount Q-RCL is smaller than the maximum fuel injection amount Q-FULL, and wherein the control means performs the normal operation when at least one of said conditions is not satisfied.