South Island Mobil petrol stations are running short of fuel.
Among those affected are the Greymouth outlet, which yesterday said it was running low, and the Murchison Mobil, which had already run out of 91 octane.
The company's manager, Andrew McNaught, said Mobil was working to organise an alternative supply.
Customers are being warned branches in some regions may, at intervals, have no regular or premium fuel.
The company blames the shortage on shipping and storage problems in the South and has apologised for the inconvenience both to its stores and customers.
A spokesperson for Z Energy says they are not having any problems with the supply of 91 in the South Island, or nationally.