The UK's major supermarket fuel retailers have cut the price of petrol below £1 a litre.
It is the first time the cost of filling up has dropped to that level since 2009, excluding promotions.
The cuts come as the price of oil continues to tumble, with Brent crude sinking below 39 US dollars a barrel.
Morrisons reduced its unleaded to 99.7p per litre (ppl) and diesel to 103.7ppl.
Tesco and Sainsbury's both announced cuts to make petrol 99.9ppl and took a penny off diesel.
The Christmas price war began when Asda launched a three-day promotion - ending on Sunday - which dropped unleaded to 99.7ppl and diesel to 103.7ppl.
Luke Bosdet, of motoring organisation the AA, said: "The question for non-supermarket forecourts is whether they ride out the storm or take it on with price cuts of their own.
"If the latter, the UK could see a serious dent in the average petrol price by the end of the weekend."
RAC Fuel Watch spokesman Simon Williams said "Christmas has clearly come early for motorists".
He went on: "Cheaper fuel at the most expensive time of year is great news for everyone, especially as many will be travelling long distances to spend festive holidays with family and friends.
"The supermarkets' decision to drop to below £1 is good news for motorists everywhere as it will help to bring the average price of petrol down across the country."
Peter Cattell, fuel director at Tesco, which has more than 500 forecourts and the largest market share for fuel retailers in the UK, said: "We want to do all we can to help our customers in the run-up to Christmas.
"We know that our customers really value low fuel prices and that having unleaded for 99.9p a litre will really give customers a boost over the festive period."