1 (wiktionary) 2 (zh.wikipedia) 3 (en.wikipedia) 4 (glosbe)

Compounds Expand your vocabulary by studying more complex words built by the 'core words'.

HSK 3.0 (2022)	Big5	Gb	Pin	Eng
3	石油	石油	shíyóu	crude, rock oil, crude oil, oil, coal oil, fossil_oil, fossil oil, petroleum
5	化石	化石	huàshí	fossil