Petrol prices have hit a two-year high, breaking the "shock horror" point of $2 a litre, the Automobile Association says.

Petrol prices rose 3 cents a litre yesterday, taking increases since September to 22c a litre. Some car owners are now paying more than $100 to fill their tanks.

Part of the 22c rise relates to the October increase in GST.

Greenstone, which operates Shell stations, put up 91 octane to $1.95.9 a litre, with its 95 octane rising to $2.02.9 a litre. Diesel rose 4c a litre to $1.32.9.

Other big petrol companies are expected to follow suit.

Small player Gull said it would hold off till next Monday, with its prices 4c a litre less than Shell.

Greenstone blamed the latest increase on the steadily rising cost of oil, which is now about US$88 (NZ$117) a barrel.

The New Zealand dollar had also weakened, making fuel imports more expensive.

Oil prices have risen because of increased demand after the severe cold in Europe this winter. There is also continued strong demand from emerging economies such as China and India.

AA general manager Mike Noon said it could see why petrol had gone up, although diesel profit margins were now at the top of the usual range in New Zealand.

"We would have expected any move on diesel to be 2c a litre, not 4c," he said.

The "psychological number" for drivers was $2 a litre. The cost of 91 octane was close to $2 and 95 octane above that mark already.

"The shock horror factor comes when they say that is so expensive ... when you fill the car up and it is more than $100 [a tank]," Mr Noon said.

Even smaller cars were costing close to $100 to fill.

"That's a lot of money close to Christmas and before holidays when people go off to drive. It is not a good time for prices to be going up."

(Source Dominion Post)