Shell has dropped the price of petrol by 3c a litre, taking it below $2 per litre for the first time since May.
From 5pm, Shell's Ultra 91 was 199.9c per litre, its 95-octane petrol 204.9c per litre, while diesel fell by 8c to 171.9c per litre.
"We have been reviewing prices daily, and despite a steady fall in the Kiwi dollar over the last week, we have seen enough drop in the price of crude to be able to pass on these savings to Kiwi motorists," said Shell spokeswoman Jackie Maitland.
Petrol has fallen by five times in the last month, and diesel by four times, despite a 5 percent decline in the New Zealand dollar.
Oil futures are currently around $US117 ($NZ169.6), well below this year's peak of more than $US147 a barrel in mid-July. Analysts believed the market was unlikely to return to those peaks soon.
