Abstract: A method and system of temperature control of heavy hydrocarbons in a consist of rail cars is disclosed wherein waste heat from one or more of the locomotives propelling the train is utilized to heat the heavy hydrocarbons in a consist or ambient air is used to cool the heavy hydrocarbon cargo. The train is typically comprised of tanker cars that can be filled with raw heavy hydrocarbon, not dilbit thus allowing about 20% to about 30% additional heavy hydrocarbon to be transported in each tanker car. The system can keep the heavy hydrocarbon at a first, lower temperature en route and increase temperature to a second higher temperature as the train nears its terminus so that the tanker cars can be quickly emptied of their contents at the receiving terminal without the need to heat the tanker cars at the unloading terminal. The method disclosed herein for heating tanker cars in transit is to utilize waste heat from the locomotive diesel or gas turbine engines which is otherwise exhausted to the atmosphere.