oil tanker 
noun
A ship designed to carry oil in bulk.The firm currently operates four vessels - three bulk carriers and an oil tanker - and has a fifth on order at Guangzhou Shipyard International....
- A Hercules aircraft homed in on the boat's locator beacon and a merchant oil tanker eventually launched a lifeboat and was rowing the man to safety, said Jessup.
- In July it reported three attempted boardings in less than a week, with pirates firing automatic weapons at two gas tankers and an oil tanker.