Dirty. This expression is regulary used in tanker freight market reports and refers to fixtures for βdirtyβ oils, e.g., fuel oil, lubricating oil and crude oil, in contrast with βclean oilsβ, e.g., gasoline, diesel oil, etc. A βdirty serviceβ is the tanker transportation of crude oil and residual fuels. A βdirty shipβ is a tanker which has been carrying crude and heavy persistent oils such as fuel oil. βDirty ballastβ is ballast that is carried in unwashed cargo oil tanks.