Castrol Perfecto HT 5 

==> based on a solvent-refined, high viscosity index mineral oil specially selected for its high thermal and oxidation stability. Application Perfecto HT 5 is primarily intended for use in closed heat transfer systems with bulk temperatures up to 300ºC. It can also be used in open systems at much lower bulk oil temperatures. Perfecto HT 5, because of its solvency and high thermal stability serves as excellent Turbine Flushing oil. Advantages Tightly controlled specification helps minimise deposits in heat exchangers in order to maintain heat transfer efficiency High operating temperature capability in closed systems with temperatures up to 300oC permitted