Oil prices ended lower by close of trade in New York, after investors locked in profits after crude oil had earlier hit record highs.
The Turkey-Kurdish situation is creating uncertainty
But analysts say the downward trend is likely to be temporary, as the factors triggering recent highs remain, notably supply fears and the lower dollar.
US light sweet crude fell 87 cents to $88.60 after an earlier $90.07 record.
And London Brent crude settled 81 cents lower at $83.79, after reaching an all-time high of $84.88 on Thursday.
"The petroleum markets are seeing some short-term profit taking," said Citigroup analyst Tim Evans following Friday's falls.
But the overall trends in recent days has been upwards, with oil prices setting new records in the wake of geopolitical tensions which have triggered fears that supplies could be threatened.
Another factor behind the rise has been the dollar reaching a record low against the euro, and a three-week low against the yen, not helped by weak US jobs and manufacturing data on Thursday.
Dollar weakness, caused by fears over the strength of the US economy, has made oil a more attractive investment.
This has increased expectations that the Federal Reserve will cut US interest rates further from the current 4.75% later this month.
The tension in eastern Turkey centres on possible military action by the Turkish army against Kurdish rebels operating from across the Iraqi border.
Earlier this week, the Turkish parliament approved a government plan to carry out excursions across the border, although imminent military action is not expected.
Oil producers' cartel Opec has hinted that it may boost output to help reduce prices.
Nigerian Oil Minister Odein Ajumogobia said Opec leaders could now meet as early as 17 November, three weeks ahead of their next planned meeting.
Oil prices have quadrupled since 2002 because of strong demand from fast-growing economies such as China and India, allied to instability in oil-producing nations in the Middle East and Africa.