Adding to concerns, the Muslim Brotherhood and hardline Salafi parties will hold protests across Egypt on Saturday in support of Mursi.
Some experts argued the risk to oil supplies could soon trump global demand woes.
"The Middle East looks set to be a major source of uncertainty in the New Year," said David Hufton, managing director at PVM, in a note.
"That provides a key support for oil prices and could well sabotage even the most persuasive set of bearish physical supply/demand figures."
Still, analysts pointed to weekly U.S. inventory data released by the Energy Information Administration to reinforce the bearish case. Gasoline stockpiles showed a near 3.9-million-barrel build last week, well over analyst expectations for a 900,000-barrel gain, as demand again trailed year-ago levels.
Stockpiles on the East Coast, where Hurricane Sandy devastated the fuel distribution network earlier this month, also rose, as did distillate inventories in the region.
A small drop in total U.S. crude inventories countered expectations of a build, but was not enough to offset the pressure of the gasoline increase, analysts said.
"Today's EIA data was bearish, with a much greater-than-expected build in gasoline stocks as refineries came back online following Hurricane Sandy," said Chris Jarvis of Caprock Risk Management in Boston, noting the draw in crude stocks was small.
"Given the robust level of crude stocks that are well over the five-year average, it was not enough to offset the bearishness in the gasoline data." (Reporting by Matthew Robinson in New York; Additional reporting by Simon Falush and Shadia Nasralla in London and Luke Pachymuthu in Singapore; Editing by Dale Hudson)