Crude oil prices rose above $80 US a barrel Wednesday as the U.S. dollar slipped and North American refineries increased production ahead of the traditionally busy summer driving season.

In New York, oil for April delivery closed up $1.19 at $80.87.

Canada is the leading supplier of oil imports to the U.S. (CBC)

The Canadian dollar also gained against the greenback, finishing at 96.90 U.S., up 0.42 cents. Canada is the No. 1 supplier of imported oil to the U.S.

Oil began moving up early in the day after Greece announced additional austerity measures and the euro rose against the U.S. dollar.

Crude is priced in U.S. currency and tends to rise in price as the dollar falls, which makes oil cheaper for investors holding foreign currency.

The rally came despite an Energy Information Administration report that said U.S. oil and gasoline supplies grew more than expected last week and remain well above average for this time of year.

The EIA also reported that refineries have increased operations for four straight weeks. America's refineries slowed operations earlier this year to some of the lowest levels on record as they struggled to pass higher oil costs along to consumers.

Now they've slowly started to bring more fuel to market. Gasoline prices are expected to increase along with demand as the weather warms and drivers do more travelling.

That expectation alone has boosted investment in oil and gasoline prices despite tepid consumer demand, said Jim Ritterbusch, president of energy consultancy Ritterbusch and Associates.

"When you get into the month of March, a lot of people start looking toward the summer," Ritterbusch said.

With files from The Associated Press