Which lubricant is typically used for light to moderate duty in high-speed pumps?

Oil is the typical lubricant used for light to moderate duty in high-speed pumps due to its ability to effectively reduce friction and heat generation at high operating speeds. It provides a thin, consistent film between moving parts, ensuring smooth operation and preventing wear. The fluid nature of oil allows it to circulate easily, promoting better cooling and lubrication in high-speed applications, which is crucial for pump performance and longevity.

Grease, while useful in certain applications, is generally thicker and may not adequately penetrate and lubricate internal components in high-speed operations. Water can be detrimental in most cases, as it lacks the necessary lubricating properties and can lead to corrosion and rust in metal parts. Gel lubricants, while offering some level of adhesion, do not provide the necessary flow characteristics required in high-speed environments. Therefore, oil is the optimal choice in this context.