Defines a method for the determination of the ageing behaviour of rust- and oxidation- inhibited mineral oils having a density less than that of water, used as turbine oils (categories TSA, TGA, TSE, TGE of ISO 6743-5, hydraulic oils (categories HL, HM, HR, HV, HG of ISO 6743-4), and circulating oils (category CKB of ISO 6743-6).