About 30 motorists in Dunedin and Oamaru encountered engine problems after filling their vehicles with contaminated petrol last Friday.
The fuel had been contaminated with water during "routine pipeline testing" at a terminal in Dunedin earlier in the day.
The contaminated 91-octane petrol was delivered to three BP sites, Regent on George St, Dunedin North on Cumberland St, and Oamaru BP, and Mobil Northgate on Cumberland St. The 91-octane fuel tanks at these stations were closed after the problem was discovered. All had since been cleaned and reopened.
BP communications and external affairs manager Jonty Mills said about 15 Oamaru customers and three in Dunedin had reported problems.
Mobil Northgate owner Beven O'Callaghan said 12 customers had experienced problems.
Mr Mills said BP had provided five rental cars to Oamaru customers, and four mechanics were brought to the site to repair affected vehicles.
Mr O'Callaghan said the contamination was noticed when vehicles that had been filled up "couldn't leave the forecourt".
"[The vehicles] that we organised to have repaired are all on the road now, with new filters and fresh fuel." A couple of customers had taken their vehicles to other workshops, which were closed for the weekend, and so were yet to get their cars back on the road.
Any others who believed they had been affected could contact any Dunedin Mobil outlet, Mr O'Callaghan said. It was "rare" for petrol to be contaminated.
Mr Mills said the petrol was believed to have been contaminated on Friday during routine testing of a pipeline at the industry terminal in Dunedin, which is owned by BP and operated by New Zealand Oil Services Ltd.
The terminal services both Mobil and BP stations in Dunedin and the surrounding area.
A couple of trucks loaded 91-octane fuel from the terminal and delivered it to the affected sites.
The terminal tank was closed at 6.30pm on Friday. The problem was rectified and the tank was operating again about noon on Saturday.
How the water entered the pipe was subject to a "full investigation", Mr Mills said.
