Various oil formulations were studied in order to ascertain their suitability for use in automobile engine applications. They are characterised according to viscosity, VI, pourpoint and Noack volatility, and the results presented for elastomer compatibility, oxidation resistance and Cu/Pb bearing corrosion, wear, groove filling and viscosity increase in engine tests. The paper concludes that a blend of PAO and polyolesters is a useful component of a SAE 10W‐30 semi‐synthetic motor oil.