56860-ZZ3-003 Oil Tank Cap - Overview. The 56860-ZZ3-003 Oil Tank Cap is an essential component designed specifically for Honda marine engine systems. Its primary function is to securely seal the oil tank, preventing leaks and contamination while maintaining optimal oil preservation. This cap plays a crucial role in keeping your engine running smoothly by ensuring the oil system remains closed and protected from external elements. Manufactured to match Honda's strict factory specifications, the