As a management level engineering officer on a motor vessel equipped with engines capable of burning both high sulfur content residual fuels and low sulfur content distillate fuels, on approaching arrival to a US port, when would you plan for the fuel changeover to be accomplished?

Correct Answer: Option A — When entering the SOx emission control area set by local authorities.

MARPOL Annex VI establishes Emission Control Areas (ECAs) to limit SOx emissions. Fuel changeover must be completed upon entering the ECA to ensure the vessel is burning compliant low-sulfur fuel. Compliance is strictly monitored, and failure to switch fuels before entering the zone constitutes a violation of international and local regulations.