Synthetic Lubricants To Increase Engine's Efficiency

[gunthaarz]

"Another problem in diesel engines can be the increased wear in outlet valve seats in the cylinder heads, because a minimum content of sulfur is not specified in MIL-DTL-83133G. Sulfur in fuels contributes normally to build up damping soot layers in these valve seats. "

Does "damping soot layers" mean that sulfur has a beneficial effect on the engine, as in lubrication or does this mean that sulfur has an adverse effect on the engines?