Many thermal treatment processes require a protection or reaction gas atmosphere. The heating is mostly realized with gas-fired jet heat pipes made of heat-proof steel and, recently, of silicon-infiltrated silicon carbide. However, if fuel oil is used instead of gas, this SiSiC jet pipe material is susceptible to corrosion due to impurities in waste gases of fuel oils. Investigations presented aimed at identifying corrosion-effecting oil components and their influence on SiSiC at high temperatures.