Which of the following is NOT a method listed for lubricating the piston pin?

• A. Drilled passages in the connecting rod
• B. Spray nozzle
• C. Splash oil from the crankcase
• D. Oil bath in the cylinder

Answer: (D)

Wrist pin lubrication relies on delivering a steady film of oil directly to the pin bearing through paths that bring oil from the crankcase to the pin area. The methods that accomplish this are splash lubrication from the crankcase, a spray nozzle that projects oil onto the pin region, and drilled passages in the connecting rod that route oil up to the wrist pin bushing. An oil bath in the cylinder, however, isn’t a practical way to lubricate the piston pin. Keeping an oil layer inside the cylinder would expose the pin to high temperatures and oil burn-off, and the oil wouldn’t be reliably distributed to the tiny bearing surface. The wrist pin requires a controlled, lasting oil supply to prevent wear, which the cylinder oil bath cannot provide.