Reason for max linear wear on top and near scavenge ports

Reasons for maximum wear at top of the stroke being:

The gas load behind the ring is maximum
It is the hottest region
Viscosity of oil film is low and liable to breakdown under heavy load and high temperature
Abrupt Change in direction of piston rings, at dead ends of reciprocating motion.
Corrosive wear
More liable to be attacked by acids.

Reason of maximum wear around the ports.

Due to leakage of hot gases past the top ring into the ports and these hot gases will tend to burn off the oil film.

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