A general structure of the specific optimal control has been previously formulated and used to solve the fuel optimal problem of an aluminum casting furnace. Proportional, integral, and derivative (P, I, D) closed-loop control were applied to a 10-order nonlinear model of the furnace. This paper analyzes the resulting control actions and the dynamic response to a step change in the target temperature of the liquid metal. It is shown that P and PD schemes are stable but bring about a steady-state error, whereas PI and PID schemes cause no steady-state error but involve considerable oscillations in the transient response and longer settling times. In view of the system's high thermal inertia and the need to impose limits on fuel flow rate, it is found that a PD scheme is the most appropriate due to the absence of overshoot and a short settling time. The method is also applied to another optimization criteria, the minimization of temperature oscillations. This shows the applicability of the scheme to practical industrial problems.