While bunkering heavy fuel, what quick/easy test can one perform onboard to determine the compatibility of 'old' with 'new' fuel?

Correct Answer: Option B — Use blotter paper with a single concentric drop of 'old' and 'new' fuel, if they do not form separate circles, the fuels may be deemed compatible.

The blotter spot test utilizes chromatographic separation. Mixing old and new fuels on filter paper reveals compatibility; if asphaltenes precipitate, distinct concentric rings or dark centers form, indicating incompatibility and potential filter-plugging risks.