Refining NZ expects its expanded petrol making facilities to be operational in late 2015.
At the company's annual meeting on Friday, 65% of shareholders approved a $365 million upgrade of an ageing petrol plant at the Marsden Point oil refinery.
Refining NZ is 73% owned by BP, Mobil Oil, Caltex, and Z Energy's owner Greenstone Energy. Of the votes they hold, 56% were in favour - it appears Mobil and Exxon voted against the upgrade.
The company expects the project to boost production by 2 million barrels per year and lift its market share from 50 to 65%.
Chief executive Ken Rivers says the company committed to some long-term purchases on Friday.
"We've got our banking facilities signed up, our foreign exchange hedges going, contracts are being signed for labour as we speak.
''We'll be clearing the ground over the course of the next year, starting to dig holes in the second half of 2013 and the big construction kicks in in 2014 through 15", he said.
Shares in the company rose 10 cents to $2.85 on Friday.