Motorists face more increases in the price of petrol, which is likely to reach a new high, the Automobile Association is warning.

Motorists are being urged to redouble fuel conservation efforts as no early end seems in sight to the price rises.

Even after two increases last week - in which petrol rose 8c a litre and diesel by between 6c and 10c - the AA says the oil companies have still not passed on the full brunt of a global cost spiral.

"So we shouldn't be surprised if there's pressure to raise prices in the coming week," senior AA analyst Mark Stockdale said last night.

All the big four suppliers have lifted the price of 91-octane petrol at city pumps to $2.11 after confusion in the market late in the week.

That was caused by BP, which found itself out on a limb after being the first to impose the latest increase, and then backed down.

But after watching its rivals leapfrog its prices on Friday and Saturday, BP followed them back up, citing unsustainable import costs.

Even though that is only 8c below the record price of $2.19 for a litre of 91-octane petrol after American oil wells were crippled by cyclone damage in 2008, Mr Stockdale said the companies had faced a 13c increase in import costs in the past fortnight.

Only Gull is undercutting the big players, selling its 91-octane bioethanol-petrol blend for $2.06 and diesel for $1.48, which is 1c below the Caltex price and 8c lower than BP.

Mr Stockdale warned continuing instability in the Middle East could push the price past the $2.19 record.

British International Development Minister Alan Duncan, a former oil trader, is warning that a barrel of crude oil could almost double to US$200 - well above a record high of US$147 - if unrest in Libya and elsewhere in the Arab world gets worse.

"All I'm predicting is danger," he told the Times newspaper.

"If crude oil doubles you're going to have a very serious spike - trying living without it for a week."

The British Government is coming under increasing pressure over prices at the pumps, which exceed $3 a litre in some districts, as 63 per cent of the revenue goes into its coffers, compared with a tax share of 43 per cent in New Zealand.

Although Mr Stockdale was not so pessimistic, he warned prices were unlikely to ease much once the latest Middle Eastern crisis abated or Saudi Arabia tried to stabilise the market by increasing its own oil production.

"We have to get used to the idea that as global demand increases and supply doesn't, we are going to be facing these kinds of price fluctuations, and whenever any little crisis comes along it's going to lead to price spikes," he said.

"The only way we can manage that is by reducing our consumption."

Although Libya is not among the largest oil producers, Mr Stockdale said the relatively small cut in production amid political upheaval in that country showed an international buffer of supply over demand was dwindling.

"This is a global issue - worldwide we need to look at supplementing consumption with renewable fuels or alternative transport."

Green Party transport spokesman Gareth Hughes said that although the AA was concentrating on giving drivers energy-saving tips, there was an urgent need for the Government to prepare the country for an oil squeeze by promoting public transport and alternative fuels.

"In 2008, when oil prices rose, we found people flocking to public transport but the system simply wasn't ready so in Wellington they had to get rail units out of the museum and Auckland had people packing the trains."

Mr Hughes said none of the Government's seven "roads of national significance", including the $1.7 billion Waterview Connection motorway project under consideration by a board of inquiry sitting in Auckland, had oil price risks factored into their business cases.

* Get regular servicing, top up tyre pressures and align the wheels.
* Don't speed - travelling at 110km/h can guzzle through 13 per cent more fuel sticking to the speed limit.
* Ease off the pedal rather than braking heavily.
* Although air-conditioning prevents drag from rolled-down windows, it can use 10 per cent more fuel so put it on the economy setting when not using it.
* Turn your engine off if you are stopped for more than 30 seconds and try to avoid peak-hour traffic.
- Source: AA