ACEA Oil Sequence evaluates several physical features, like foam formation tendency, pumpability at low temperatures, evaporation and the HT-HS value. HT-HS is an acronym for High Temperature, High Shear. This latter value is a relevant feature in the understanding of ACEA ratings. HT-HS test measures oil viscosity at 150°C undergoing high mechanic stress. It basically recreates the lubrication conditions of the bearings. A low HT-HS value (below 3,5 cP) is synonym of thin engine oil meatus. A thin meatus means less friction between mechanic parts and therefore less fuel consumption.
Does it mean that everybody can freely choose an engine oil with fuel economy properties? The answer is no. Only engines specifically made to support these low HTHS oils could benefit from fuel economy fluids, otherwise the oil meatus risks to break leading to wear and breakages.
