Continuous operation at Mach 2 means higher oil system temperatures than in conventional aircraft powerplants. Consequently, a new type of lubricant is required and new methods of evaluating lubricants. The main requirements for a lubricant for the Concorde engines are defined in terms of bulk thermal stability, resistance to breakdown in a hot bearing, oil mist coking and gear load carrying. The rigs used to evaluate these various properties are described in detail, and some of the reasons for the choice of these particular rigs are given. Problems which may arise on mainshaft bearings are split into two groups, fatigue at high load and wear due to skidding at low load. The test rigs and methods used to explore both these phenomena are described. It is claimed that fatigue is relatively well understood but skidding at low loads is a much more complex matter and there is scope for more work to establish the important parameters. Minor lubricant problems have arisen on early standards of engine but these have now been overcome and performance of the oils is satisfactory. It is therefore concluded that the oil evaluation methods are successfully screening out unsatisfactory oils.