Oil climbed to within 50 cents of its all-time high as US refinery outages hampered efforts to meet strong demand growth in the world's biggest consumer.

US light sweet crude rose 66 cents to $62.04 a barrel, 46 cents below the record high hit on Wednesday at $62.50 a barrel.

London Brent crude gained 76 cents to $60.88 a barrel, 38 cents off the record-high of $61.26.

"It's no secret that refineries are the problem. There wouldn't be a problem if there was any slack in the system," said Tony Nunan, a manager at Mitsubishi's international energy business in Tokyo.

A half-dozen refineries in the United States have been forced into unplanned shutdowns since late July and some have had to delay planned restarts, leaving the market on edge after US gasoline stocks fell a sharp four million barrels last week.

Inventories have fallen into the lower half of their seasonal average, while demand is running 1.1 per cent stronger than last year with a month left in the summer.

Supplies of distillates, which include heating oil, rose 1.5 million barrels to stand almost 3 per cent higher than a year ago, but even stronger demand growth for these fuels coupled with refinery trip-ups could dent supplies before winter.

"Demand is so high and capacity is so low, we can go from comfortable to uncomfortable inventories within a month," Nunan said.

Sunoco's refinery in Toledo, Ohio, failed to restart on Thursday, while the restart of Exxon Mobil's plant in Joliet, Illinois, was expected to be delayed, trade sources said.

They said BP had delayed restarting its downed fluid catalytic crackers at its Texas City, Texas, refineries.

Additional disruption could come from an unusually active Atlantic hurricane season, which has already produced eight named storms and could culminate in as many as 21 tropical storms and 11 hurricanes, US government weather forecasters have said.- (Reuters)