However, strong overall demand for oil especially from refineries, as well as supply disruptions, were helping to keep prices from falling faster and further.
"Despite falling slightly overnight, the outlook for oil (prices) remains positive, which should keep the recent upward trend intact," ANZ added.
Crude prices have virtually doubled since touching their lowest in more than a decade in early 2016 as strong demand and supply disruptions erode a glut that pulled down prices by as much as 70 percent from a mid-2014 peak.
Market rebalancing is ongoing. On the demand side, global refining activity is about to hit its highest on record just as crude supply disruptions around the world tighten the market.
Data in Thomson Reuters Eikon shows that currently available global refining capacity will reach 101.8 million barrels per day (bpd) in August, its highest on record, and up from around 97.25 million bpd in March.
Of the available capacity, investment bank Jefferies said on Friday that U.S. refinery utilization alone reached 90.9 percent in the first week of June.
Traders said this means producers need to pump every barrel of crude they can to meet refinery demand, and that the supply disruptions around the world - from Canadian wildfires, sabotage in Nigeria, and output cuts in the United States, Venezuela and Asia - will tighten the market and eat into inventories.
Yet the strong refinery output could end as fast as it came as the reserve capacity, the difference between available and installed capacity, is about to fall below half a million bpd, the tightest since late 2013, the data shows.
"Refining output, and by extension crude demand, can basically only go down as facilities either go into unplanned outage or refinery runs are cut to reduce an emerging product glut," said one trader in Singapore.