[Eric in the Ozarks]

Sulfur content in fuel is a big issue in big marine engines. These engines also consume a portion of the lube oil and the combination can produce acids that attack bearing surfaces.
There are about 79 thousand ships in the world's merchant fleets. They operate mostly on heavy oil but there is some evidence of a move toward more expensive low sulfur diesel. This cost is partially offset by reducing cruising speed from 25 knots to 18-20 knots.

[thackney]

But isn’t that stuff more than 500 ppm, except in the states?

I was thinking US gasoline was already so low in sulfur the users would not notice a difference.