Crude oil prices have fallen for the second day and are now down by $5 a barrel since a government report showed that US petrol reserves had increased.
US drivers have had to cope with soaring petrol prices
Concern that gasoline supplies would not be able to meet demand during the summer holiday months has been one of the factors underpinning record prices.
New York's main contract light crude shed $2.88 to $69.40, while London's Brent crude slid $2.49 to $70.16.
US petrol prices have fallen below $2 for the first time since 11 April.
The Energy Information Administration (EIA) said on Wednesday that petrol stocks in the US rose by 2.1 million barrels last week.
Analysts said that the increase, the first since February, may have been down to consumers driving less because of higher petrol prices.
"I think high prices, without question, are starting to have an effect on demand," said Bill O'Grady, an analyst at AG Edwards.
However, the EIA said that geopolitical tensions and concerns about a clash between the US and Iran over the latter's nuclear programme are likely to underpin oil prices in coming months.
This view was echoed by market watchers.
"I don't think we will see oil fall below $65 anytime soon because of Iran and Nigeria," said Michael Lynch from Strategic Energy & Economy Research.
Oil company Royal Dutch Shell says unrest in Nigeria has stopped output of 455,000 barrels of oil a day from its facilities since the end of March.
The downward trajectory of oil prices helped send markets higher in the US and across Europe on Thursday.