Sagawa, T., Nakano, S., Bito, Y., Koike, Y. et al., "Development of Low Viscosity API SN 0W-16 Fuel-Saving Engine Oil Considering Chain Wear Performance," SAE Int. J. Fuels Lubr. 10(2):2017, doi:10.4271/2017-01-0881.
A low viscosity API SN 0W-16 engine oil was developed to achieve a 0.5% improvement in fuel efficiency over the current GF-5/API SN 0W-20 oil. Oil consumption and engine wear are the main roadblocks to the development of low viscosity engine oils. However, optimization of the base oil and additives successfully prevent oil consumption and wear. First, it was confirmed in engine tests that NOACK volatility is still an effective indicator of oil consumption even for a low viscosity grade like 0W-16. As a result of base oil volatility control, the newly developed oil achieves the same level of oil consumption as the current GF-5/API SN 0W-20 oil. Second, it was found that the base oil viscosity and molybdenum dithiocarbamate (MoDTC) had a significant effect on chain wear in rig testing that simulated silent chain wear. For the same base oil viscosity, the new oil maintains the same oil film thickness under high surface pressure. The same base oil as that of the current GF-5 0W-20 oil was selected to obtain that oil film thickness. Viscosity was adjusted by reducing the viscosity modifier content. Additionally, the anti-wear performance of MoDTC was confirmed not only with fresh oil, but also with aged oils that were collected after actual vehicle tests. MoDTC reduced friction and wear with fresh oil, but aged oils showed high friction and low wear. This indicates that some MoDTC decomposition products do not have a friction reduction effect, but they reduce wear. As a result of optimizing the base oil and additives, the anti-wear performance of the new oil was assured.