Systems and methods for regulating an outlet coolant temperature of a genset and an inlet coolant temperature of the genset are provided. A load condition of the genset may be determined. An operating mode can be selected from between a first mode associated with a first load condition and a second mode associated with a second load condition responsive to determining the load condition of the genset. The first mode and the second mode may be configured to determine a target inlet coolant temperature using one or more control loops. The target inlet coolant temperature may be determined using the selected operating mode, a target outlet coolant temperature and the outlet coolant temperature. The outlet coolant temperature may be regulated based on the determined target inlet coolant temperature and the inlet coolant temperature by adjusting an operation of one or more coolant valves.