THE only fuel property showing significant correlation with wear and deposits in these tests was sulfur content.
Work on two engines: one operating at a moderate bmep and speed, the other at high bmep and high speed, showed that the more heavily loaded engine consumed three times more fuel per hour, per cylinder than the moderately rated engine and the increase in wear for a ½% increase in sulfur was also three times that encountered in the moderately rated engine. This indicates that high rates of wear and more deposits encountered at high bmep and speeds are not so much a function of the higher mechanical and thermal loading of the parts, but are primarily due to the fact that more fuel is required to carry the higher loads.
It is the opinion of the authors that sulfur combines with the hydrocarbon molecules of the fuel in the combustion process and forms a black abrasive deposit that causes wear.