Abstract: A fluid heating system and method are disclosed. The apparatus incorporates a two-stage heating system. The first stage uses heat produced by a large, primary heat source, such as a diesel engine. The primary heat source is used to heat a coolant solution contained within a closed loop. The first stage uses one or more high-efficiency liquid-to-liquid heat exchangers. The second stage transfers thermal energy from the heated coolant solution to a secondary fluid. The second stage uses a high-efficiency liquid-to-liquid heat exchanger. The secondary fluid is heated to a temperature suitable for an intended purpose. The secondary fluid may contain petroleum products that may coagulate at low temperatures. Heating such a fluid may be needed for processing of the fluid. By using an intermediary closed coolant loop, the primary heating fluid or fluids are contained in a separate flow loop from the secondary fluid.