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A novel ultrasonic viscometer for in-situ applications in engine components is presented. The viscosity measurement is performed by shearing the solid-oil contact interface by means of shear ultrasonic waves. Previous approaches to ultrasonically measure the viscosity suffer from poor accuracy owing to the acoustic miss-match between metal component and lubricant [1]. The method described overcomes this limitation by placing an intermediate matching layer between the metal and lubricant. Results are in excellent agreement with the ones obtained with the conventional viscometers when testing Newtonian fluids. This study also highlights that when complex mixtures are tested the viscosity measurement is frequency dependent. At high ultrasonic frequencies, e.g. 10 MHz, it is possible to isolate the viscosity of the base, while to obtain the viscosity of the mixture it is necessary to choose a lower operative frequency, e.g. 100 kHz, to match the fluid particle relaxation time.

The global commitment to reduce CO2 emissions drives the automotive industry to create ever more advanced chemical and engineering systems. Better vehicle fuel efficiency is demanded which forces the rapid evolution of the internal combustion engine and its system components. Advancing engine and emission system technology places increasingly complex demands on the lubricant. Additive system development is required to formulate products capable of surpassing these demands and enabling further reductions in greenhouse gas emissions. This paper reports a novel method of generating fundamental structure-performance knowledge with real-world meaning. Traditional antiwear molecule performance mechanisms are explored and compared with the next generation of surface active additive system (SAAS) formulated with only Nitrogen, Oxygen, Carbon and Hydrogen (NOCH).