Infratil says it has not decided whether to stick with the Shell brand, though a review of its position in the market is nearing completion.
Infratil bought Shell's assets, which include 200 petrol stations, for about $700 million in March, in partnership with the New Zealand Superannuation Fund.
The Shell business, since-renamed Greenstone Energy, as well as Infratil's Australian energy company, helped the infrastructure investor to a profit of $16 million in the six months to the end of September.
That's a turnaround from a loss of $31 million in the same period last year, when it was hit by one-off asset writedowns and revaluations.
Chief executive Marco Bogoievski says the fuel market has remained relatively flat, with petrol volumes declining 1.5% and diesel rising 1.5%.
But Mr Bogoievski says Greenstone's volumes have grown 4% and the business is performing better than expected.
Gross earnings rose by a quarter to $258 million and Infratil lifted its full year earnings forecast to betweeen $415 - $435 million due to the strong first half of the year.
Infratil's shares fell 1 cent to $1.89.