Abstract
Lubricity, defined as the potential of a lubricant for minimization of wear, can be correlated with viscosity and chemical reactions. Viscosity can be affected simply by dilution with fuel, whereas chemical reactions such as with fuel combustion products can change the characteristics of the engine oil dramatically. Due to regulations increasing the bio content in fuels, the impact of ethanol and its combustion products on the wear behaviour of engine components is in the focus of current investigations.
For clarification of the correlations between combustion products and wear behaviour an appropriate measuring method first has to be applied and evaluated. Such a method can only be realised by means of radioactive isotopes to achieve the needed resolution in wear height or volume. In the second step, the lubricating performance of engine oil, which has been artificially aged by continuous addition of different combustion products, was investigated in tribometer tests with this wear measurement method. In the third step, the effects of the combustion products were evaluated in engine bench tests by admixture of different products into the engine oil circuit while using the same wear measurement method. The results provide an insight into the complicated interrelations between fuel, engine oil and wear of engine components.
KEYWORDS: engine oil, bio-ethanol, ethanol combustion products, wear measurement, radioactive isotopes