Which ring face material is used on compression rings to aid upper cylinder wall lubrication?

Which ring face material is used on compression rings to aid upper cylinder wall lubrication?

• A. Chromium
• B. Molybdenum
• C. Tungsten
• D. Nickel

Answer: (B)

A molybdenum-based coating on the compression ring face acts as a solid lubricant, reducing friction between the ring and the cylinder wall. This helps maintain a thin, consistent oil film on the upper cylinder wall during the high-pressure compression stroke, which in turn lowers wear, reduces scuffing, and improves oil control. While chromium, nickel, and tungsten coatings mainly provide wear or corrosion resistance, they don’t offer the same friction-reducing, oil-film–enhancing effect as molybdenum, making it the best choice for aiding upper cylinder wall lubrication.

A molybdenum-based coating on the compression ring face acts as a solid lubricant, reducing friction between the ring and the cylinder wall. This helps maintain a thin, consistent oil film on the upper cylinder wall during the high-pressure compression stroke, which in turn lowers wear, reduces scuffing, and improves oil control. While chromium, nickel, and tungsten coatings mainly provide wear or corrosion resistance, they don’t offer the same friction-reducing, oil-film–enhancing effect as molybdenum, making it the best choice for aiding upper cylinder wall lubrication.