Composition and oxidation stability of SAE 15W-40 engine oils

The modified IP 48 procedure was used for testing the oxidation stability o f engine oils for ignition engines of the SAE 15W-40 and minimum API SG/CD specifications. Eight engine oils, such as Agip, BP, Esso, Mogul, OMV, Petr o-Canada, Shell, and Total, were collected and oxidised. Oils were also fra ctionated by using chromatographic methods, and group composition of base o ils, amount of VI improvers and other additives were determined. Several di fferences in the oxidation stability were found between the collected oils. Viscosity characteristics, carbon residue, acid number, amount of pentane insolubles and mass losses during the test were chosen as parameters for ev aluation of the oxidation stability of the oils. The most stable engine oil was blended from a hydrocracked base oil whereas most of the other oils we re based on the solvent refined oils. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.