• 石油せきゆ — petroleum
• 油絵あぶらえ — oil painting
• 油田ゆでん — oil field
• 油断ゆだん — negligence, carelessness
• 油脂ゆし — oils and fats
• 醤油しょうゆ — soy sauce

The kanji 油 combines the water radical with 由, originally depicting a source or origin. Together they convey the idea of a flowing, extractable liquid — like oil. It appears in many cooking and industrial terms.

油あぶらを使つかって料理りょうりします。
I cook using oil.

油断ゆだんすると失敗しっぱいしますよ。
If you're careless, you might fail.