The "Gas fueled LPG" notation covers internal combustion engines, boilers and gas turbines for both gas-only and dual-fuel operations.

Nautilus members have also highlighted a range of safety and operational concerns, including incidents of power loss when changing fuels, lubrication issues.

An EPA spokeswoman said the agency "hopes to finalize the rule this winter."

The GSP was now valid until December 31, 2024, the MPA said.

Increased blending due to IMO 2020 likely to spur bunker fuel quality issues.

"We don't know what's behind this decision by the Malaysian Marine Department, but it was not likely science-based," Kaczmarek said.

"It will be a bumpy ride in the next six months but I am sure that things will stabilize thereafter," Thomsen said.

Under a no-deal Brexit UK fuel import tariffs will be set at 0%, while fuel export tariffs would rise to between 3.5%-6.5% for exports of gasoline, gasoil, fuel oils, lubricants, FAME.