Who introduced refined oil?

The Chinese geographer, writer, and statesman Li Daoyuan developed refined oil in the late Northern Wei Dynasty (512-518 AD).

In his famous book Commentary on the Water Classic, he described the process of refining oil into various lubricants.

It is created by eliminating contaminants from crude oil like free fatty acids & waxes using methods such as neutralisation, bleaching & deodorization

With the invention of industrial-scale refining methods in the early twentieth century, refined oil became readily available.

Hindustan Unilever introduced the first refined oil in India under the Dalda brand in 1937, which was a huge success and popularised the usage.