Lubricity is a term used to describe the ability of a compound (lubricant) to reduce friction between moving parts in a machine or mechanism. In many cases, the lubricant is a heavy oil or grease that coats and acts as a cushion between parts. In some cases, thin oil is forced, under pressure, into precision-machined spaces (such as bearing journals), and acts as a support between parts. Still in other cases, the lubricating compound is suspended in a liquid (such as sulfur in diesel fuel), and momentarily reduces friction before it is whisked away.
The Alternative Fuel Bible: Find Answers to Your Fuel & Vehicle Questions
Modern diesel fuel (ULSD
) has lost much of its natural lubricity because of its reduced sulfur content.