Oil refiner and marketer Viva Energy has debuted on the ASX, raising about $2.6 billion in Australia’s biggest initial public offering in nearly four years.

The stock opened at 1200 AEST on Friday at $2.43, which represents a 2.8 per cent discount to the issue price of $2.50 and values the company at about $4.7 billion.

Global energy trader Vitol retained a 45 per cent stake in Viva, which was formed in 2014 following the sale of Shell’s service stations and Geelong refinery.

The float was the largest in Australia since the privatisation of Medibank in 2014.

Viva has more than 900 Shell-branded service stations and employs more than 1,300 people, while its refinery in Victoria is one of only four in Australia.

The refinery supplies more than 10 per cent of Australia’s fuel and more than 50 per cent of all the fuel used in Victoria.

According to Vitol’s website, the Geelong refinery is the only Australian facility manufacturing bitumen and the ‘avgas’ aviation fuel used by piston-engined planes.