Russia is set to suffer the biggest revenue losses from rules mandating cleaner marine fuels from 2020, because the world’s top exporter of the sulfurous residual oil that powers ships doesn’t look prepared for the change. Refineries across the world are bracing themselves for the once-in-a-generation shift intended to reduce pollution caused by ships. While plants in Europe and the U.S. Gulf Coast seem well positioned to make the change to low-sulfur output, Russian companies have done little to prepare.