According to Paul M. Eldridge :

In addition, the sulphur content in home heating oil is significantly
higher than that of on-road diesel -- upwards of 5,000 ppm, whereas
ULSD is limited to 15 ppm or less. Marine diesel, or what is commonly
known as "Bunker C", is the dirtiest of all; it can reach as high as
45,000 ppm! [Something to think about when you book your next holiday
cruise.]

As I recall, Bunker C is also considerably heavier than regular diesel
fuel. Even at only modest temperatures, it has to be preheated to
get it to flow.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.