Oil prices have reached the highest level in four years but the value of the New Zealand dollar has stopped petrol prices here from hitting a new high too.

Petrol prices rose three cents a litre in March, with diesel up two cents a litre, after a rise in commodity prices and a drop in the New Zealand exchange rate since the last retail increase in late February.

Fuel prices have reached $2.20 a litre for 91 octane, not far off the previous high of $2.22 in May 2010, and $1.57 a litre for diesel.

AA Petrol Watch spokesperson Mark Stockdale said oil prices had peaked at US$128 a barrel during March.


He said the imported cost of petrol and diesel had risen five cents per litre while retail prices were up by 3 per cent.

"This is the highest oil price since July 2008 and higher than May 2010 when retail prices peaked at $2.22 a litre. Only the fact that the Kiwi dollar is worth more today has stopped petrol prices from hitting a new record high," he said.

Although commodity prices were lower than in mid-2008, today's retail prices were similar because consumers were paying 12 cents a litre more in petrol tax than in 2008.

Financial experts say oil prices to have a knock-on effect at the petrol pump.

OMFinancial head of financial markets Kevin O'Sullivan tipped the price per litre of 91 octane to reach $2.25 before the end of the month, in part caused by US President Barack Obama's call for sanctions on Iran.

"If the markets continue as they are, I would say it would reach $2.25 a litre in two or three weeks."

He said the the price of crude oil would track higher, flowing through to petrol prices providing the New Zealand dollar didn't go higher.