Oil companies say the fuel situation in Christchurch following Tuesday's earthquake should ease in coming days as roads are cleared and local bulk-fuel terminals resume supply.
City service stations have had to truck fuel in since the quake from Dunedin, Timaru and Nelson.
BP says it has given up telling people which service stations are open and which are not because the situation changes very quickly.
The company says demand has been heavy and service stations have to wait for long-distance tankers to arrive over damaged roads to top up their tanks.
BP says it has had to give priority to emergency vehicles and ration other motorists to $40 worth of petrol or diesel to make sure everyone has some fuel in their tank.
Mobil says the situation should ease further when its fuel terminals at Lyttelton and Woolston come back on line.
Both depots have been out of action since the quake took out the power and the water supplies needed for emergencies.
Mobil says it is working with Civil Defence to sort out an alternative water supply for the bulk fuel depots and if motorists can be patient for a little longer, fuel should be less problematic by next week.
A Shell spokesperson said fuel was coming into the city regularly, and people should buy only the fuel that they needed immediately.