An internal combustion engine system, including a primary fuel tank that stores a fuel, a fuel reformer that reforms the fuel from the primary fuel tank, a secondary fuel tank that stores the fuel reformed by the fuel reformer, a fuel injection device that injects the fuel that is selectably supplied from either the primary fuel tank or secondary fuel tank into a combustion chamber, a sensor that detects the quantity of fuel remaining in the secondary fuel tank, and a control device that sets and outputs a load and revolution speed of the engine. The control device is configured to set the engine load and engine revolution speed according to a request output determined based upon an operation performed by an operator. The engine load and engine revolution speed when the quantity of fuel remaining in the secondary fuel tank is more than a predetermined value, are set different than when the quantity of fuel remaining in the secondary fuel tank is less than the predetermined value.