The order, which was first issued on Nov. 19, limits vehicles deemed "non-essential" by the government to 30 liters (7.9 U.S. gallons) of gasoline or diesel fuel per trip to a filling station.
The restrictions will be extended through Dec. 14 as part of a state of emergency in the flood-hit province, Mike Farnworth, British Columbia minister of public safety and solicitor general, told a news conference.
"The fuel conservation measures are working but with another storm on its way, we are extending the order to ensure that we prioritize emergency services for another two weeks," Farnworth said. "This recovery will take time."
Officials have restricted travel on several major routes in the area and another, Highway 1, remains closed.
Four people were killed and Canada's Pacific province is facing billions of dollars of damages after an atmospheric river dumped a month's worth of rain in two days on southern B.C, triggering mudslides and wash-outs that destroyed road and rail routes between the mountainous interior and the coast.
Evacuations have been ordered after weather forecasters predicted that the third in a series of strong storms would pummel British Columbia on Tuesday.
(Reporting by Dan Whitcomb; Editing by Dan Grebler)