油
yóu · HSK 2
oil
🛢️ yóu sounds like 'yo!' — oil drum says yo when you slap it
由 (yóu, cause/from) gives the sound; 氵 (water radical) marks it as a liquid. So 油 = liquid + yóu-sound = the flowing stuff: oil, fat, grease.
油 — water radical 氵 + 由 (yóu, phonetic)
油 is a phono-semantic compound. The 氵 radical signals a liquid, while 由 supplies the sound. Originally referring to a river name, it was extended to mean oil or fat — any thick, flowing liquid — which became its dominant modern sense.