The most common heater of an industrial engine is for the jacket water. Keeping the entire block heat soaked is the easiest/safest way to heat the oil as well.

The most common heater of an industrial engine is for the jacket water. Keeping the entire block heat soaked is the easiest/safest way to heat the oil as well. Using a "prelube pump", which is a low pressure, low volume circulation pump that parallels the main engine driven pump, oil is continuously sent throughout the internal passages