Low viscosity combined with appropriated additive technology is one of the main paths to reduce friction on Internal Combustion Engines. Japan is on the cutting edge of low viscosity oils, having already available SAE 0W-8 in the market. On the other hands, in emergent countries like Brazil, SAE 15W-40 is still used in some passenger cars while the Japanese origin car brands use SAE 0W-20. Lubricant friction additives type also differs depending on the original equipment manufacturer (OEM) origin, and the Japanese ones usually containing high amounts of the Molybdenum type. In this paper, some of the advantages and challenges of using low viscosity oils are discussed and emphasis is given in the friction reduction obtained with the synergic effects of the right choice of additives components type and the material/coating used in the engine parts. Ring-liner rig and floating liner engine tests comparing different oils will be presented. Detailed lubricant tribofilm analysis help to explain the complex tribo-chemical phenomena with different oils.
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