Green’s Dictionary of Slang

oil tanker n.

[rhy. sl. = wanker n. (2)]

a general term of abuse.

[UK]R. Puxley Cockney Rabbit.
[Ire]P. Howard Curious Incident of the Dog in the Nightdress 37: There’s, like, two kids [...] the one who called me an oil tanker and then another.