A 1964 antedating supplied by Bryn has been verified.
Add oil is an expression that has gained a lot of currency in Hong Kong in the last few years. A literal translation of the Cantonese phrase ga yao, it is used by Hong Kongers as an exclamation expressing encouragement or support. OED editors are currently researching the term, with an intention to publish in a future update.
So far, the earliest definitive evidence we have found is from the South China Morning Post of November 2005:
When a mainland Chinese athlete stepped into the arena, some children mistakenly thought he represented Macau and started chanting: ‘Macau team, add oil!’
2005 South China Morning Post (Hong Kong) 1 November (Macau Notes section) p. 2
However, several sources suggest that the expression originated as a cheer at the Macau Grand Prix in the 1960s. Can you help find any printed examples of add oil from before November 2005?
Posted by OED_Editor on 17 May 2016 15.00