The effect of engine and transmission oil viscometrics on vehicle fuel consumption

J. Gary Hawley, Chris D. Bannister, Chris J. Brace, S. Akehurst, Ian Pegg, M. R. Avery

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An extensive programme of work has been undertaken to assess the potential benefits of modulating the properties of both the engine and the transmission lubricating oils to achieve lower fuel consumption. The performance of the engine lubricants was evaluated on a production diesel engine on a transient test bed. The main engine lubricating-oil viscometric properties investigated were the cold cranking shear, the kinematic viscosity at 100 degrees C, and the high-temperature high-shear value. Up to 3.5 per cent fuel economy improvement was observed over the New European Drive Cycle (NEDC), relative to current production lubricants. A model relating the fuel consumption to the oil properties was developed and verified using an experimental programme conducted on a chassis dynamometer. In a related study, the effects of changes in the transmission lubricant properties were evaluated using a standard five-speed manual transmission fitted to a light-goods vehicle and tested on a chassis dynamometer. The lubricant was heated using an external energy source to simulate the effect of a more rapid warm-up; this reduced the viscosity of the lubricant and a fuel consumption improvement of 0.7 per cent was demonstrated over the NEDC from a 25 degrees C start. In addition, a lower-viscosity lubricant blend was evaluated, which delivered a 1 per cent improvement in the fuel economy over the standard blend from a cold start, and a further 0.4 per cent improvement if heated.
Original languageEnglish
Pages (from-to)1213-1228
Number of pages16
JournalProceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering
Issue number9
Publication statusPublished - 1 Sept 2010


  • cold cranking shear
  • kinematic viscosity at 100 degrees C
  • vehicle fuel consumption
  • engine oil viscometrics
  • high-temperature high-shear value
  • transmission oil viscometrics


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