oil has 12 distinct synonyms spread across 4 of its 6 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a slippery or viscous liquid or liquefiable substance not miscible with water
oil paint containing pigment that is used by an artist
a dark oil consisting mainly of hydrocarbons
cover with oil, as if by rubbing
“oil the wooden surface”
Synonyms, antonyms and the broader and narrower relations for oil come from Princeton University’s WordNet. Full sources and licences.