One fund manager, who requested anonymity, said that while the deal was a boon for shareholders it was not such good news for consumers as Z had already been pushing back against competition to improve margins and maximise returns.
He cited government figures that show fuel importer margins have risen by about 40 per cent since January 2013, while New Zealand also has the second-highest petrol prices, before tax, in the OECD group of developed countries.
"As a shareholder you're pretty happy with this but the market seems to be acting like there's no [Commerce Commission] risk here."
Another market source, who also did not want to be named, said importer margins already suggested the fuel market was not competitive enough and the Commerce Commission should pay attention to yesterday's share price rally as an indication of the benefits investors saw in the deal.
"They should be thinking - why has the stock market taken this share up 21 per cent? It's massive."
Chevron New Zealand operates 146 Caltex and Challenge service stations, 136 of which are run by independent franchisees, as well as 73 truck filling sites.
It reported a net profit of $43 million from gross operating revenue of $2.2 billion last year.
Z already has more than 210 service stations and 92 truck stops and the acquisition will boost its share of the total fuel market to 49 per cent from about 28 per cent at present.
The purchase, which also requires Overseas Investment Office approval, includes a two-million-barrel oil inventory, 10 terminal assets and Caltex's lubricants business.
It will be funded by existing cash, debt and a $185 million pro rata capital raising that Z intends to carry out after it has received Commerce Commission clearance.
The firm is aiming for a settlement date of November 30.
Z chief executive Mike Bennetts said the Caltex sites would remain a "differentiated offer" and would not be rebranded as Z.
The firm was confident that the acquisition would not reduce competition, he added.
"We wouldn't have come into this transaction unless we were confident it wouldn't lead to a lessening of competition," Bennetts said. "We've got a good proposition here and we look forward to working with the Commerce Commission and providing them with the facts of that."
He said the company had delivered a "pretty fulsome" application to the competition regulator.
"We've also backed that up with some econometric analysis that statistically proves that there is no lessening of competition when it comes to retail service stations, either on a two-kilometre or a five-kilometre radius."
Z said it expected the purchase to be earnings-accretive from day one and provide synergy benefits of between $15 million and $25 million annually from 2017 onwards.
Craigs Investment Partners head of private wealth research Mark Lister said the purchase would be transformational for Z.
"It gives them some real scale," Lister said. "The market obviously views it favourably."
The acquisition announcement follows Chevron's sale last week of its 11.4 per cent stake in Marsden Pt oil refinery operator Refining NZ, which fuelled speculation that the company may also look to offload its service station operations in New Zealand.
In March Chevron sold its 50 per cent stake in Caltex Australia.
Chevron Corporation said in March that it planned to sell US$15 billion ($21 billion) of assets over the coming three years to maintain shareholder dividends in the face of low oil prices.
