The price of petrol has gone up and now sit at $2.21 for 91 Octane.

Z raised the price of all fuels two cents a litre on September 29, the second increase for the month of September.

The price of petrol has risen to $2.21 a litre, while diesel is sitting at $1.51 a litre.

This is in spite of oil prices falling to their lowest level in two years, although commodity prices for petrol and diesel did not fall as much, says AA spokesperson Mark Stockdale.

'At the same time, the NZ dollar has fallen over 4c during the month (to its lowest level in just over a year), more than offsetting the small reductions in refined fuel commodity prices.

'The net effect is that, since the last rise in retail prices at the start of the month, the cost of importing petrol has risen over 2c/litre.

'But the imported cost of diesel is about the same, due to a bigger drop in commodity prices than petrol, so no increase in retail diesel prices was warranted in our view.”

Mark says this will be confusing to motorists who were probably expecting prices to fall, but this illustrates the folly of monitoring (irrelevant) oil prices instead of the actual commodity prices for refined fuels – plus the effect of the exchange rate on the cost of importing fuel.

'It's also worth noting the last time the exchange rate was this low, we were paying $2.25/litre for 91 octane and $1.60/litre for diesel – but commodity prices were higher although taxes were lower too.”

The price of 91 Octane is sitting at $2.21, 95 Octane is $2.29 and diesel is sitting around $1.51.