The supermarket chain entered a 50-50 joint venture with Caltex that will result in the re-branding of around 450 petrol stations (including about 10% of Caltex's portfolio or 160 stations) to take on the 580 Coles-Shell outlets.

The new venture is already looking at revenues of about $3.5 billion a year based on current figures and will offer a 4c-a-litre discount for Woolworths, Safeway and Big W customers spending more than $30.

Fuel supplies will be sourced from Caltex refineries in NSW and Queensland while in other states Caltex will source the best-priced fuel for the JV.

Caltex will also manage the joint venture sites bringing to bear its expertise in petrol retailing and convenience store execution.

"We expect there will be a significant increase in fuel throughput at the sites Caltex brings to the JVC as Woolworths' customers redeem discount vouchers," said Roger Corbett, Woolworths group managing director and CEO.

The joint venture is subject to ACCC review, regulatory approvals and third party Consents, however operations are expected to begin before Christmas.