What does the Australia saying good oil mean?

The Australian phrase "good oil" means "reliable information" or "the truth." It is often used in informal contexts, such as conversations between friends or colleagues. For example, someone might say "I've heard on the good oil that the company is planning to lay off staff" to mean that they have heard a reliable source that the company is planning to lay off staff. The phrase can also be used to describe something that is good news, such as "I've just heard on the good oil that I got the job!"

The phrase is thought to have originated in the Australian mining industry, where it was used to refer to information about the location of oil deposits. However, it is now used more generally to refer to any kind of reliable information.