油管 has two distinct meanings. The literal sense is 'oil pipe/tube' — a physical conduit for petroleum or lubricants. In internet slang, 油管 is a widely used transcription of 'YouTube', borrowed via the English word 'tube' (管) and used colloquially in Chinese social media and online discussions. Context tells you which meaning is intended: an engineering article uses the literal sense, while a comment about watching videos uses the internet sense.