A system for reforming a fuel may include a first sensor configured to measure an operating parameter of an engine. The operating parameter may correlate to a NOx emission level of the engine. The system may also include a controller in communication with the sensor and a reformer. The controller may be configured to determine a target NOx emission level for the engine. The controller may be also configured to determine a target value of the operating parameter corresponding to the target NOx emission level. The controller may be further configured to control the reformer to reform at least a portion of the fuel based on a difference between the measured value and the target value of the operating parameter.