The Canadian dollar on Friday briefly touched 80 cents US, territory it hasn't seen in about 10 months.

The loonie's rally has seen it rise about 12 cents against the U.S. greenback since January, including a gain of 2.75 cents in April. The dollar finished Friday flat at 79.69.

The loonie's rise has been propelled by a rise in the price of oil, while the U.S. dollar has been weakening against major currencies. The U.S. greenback touched an 18-month low on Friday against the Japanese yen and lost ground against the euro.

BMO Capital Markets said the run-up in the price of oil has accounted for least half of the loonie's recent appreciation.

The price for benchmark North American crude oil finished Friday down 11 cents US at $45.92 US per barrel, although, for the month of April, the price for West Texas Intermediate (WTI) gained just over 20 per cent.

Oil bottomed out back in January around $27 a barrel.

In a Friday commentary, Scotiabank Economics said oil prices are forecast to continue rising. Scotiabank sees WTI reaching $45 to $50 US per barrel by the end of the year, but pointed out it sees a risk of a near-term retreat.

"We do not believe that the current pace of appreciation — driven more in our view by financial activity rather than slower-moving fundamentals — is sustainable," said Rory Johnston, Scotiabank economist and commodity market specialist.

"Prices may fall again before continuing their gradual path back to finding new equilibrium levels," Johnston said.

The Canadian dollar, which hasn't closed above 80 cents since June 30 of last year, is "the third best performing major currency this year, just behind the yen and Brazilian real," said BMO Capital Markets economist Sal Guatieri in a commentary.

BMO Capital said the loonie could still gain a bit more, but it sees the dollar pulling back to the 75 to 77 cent range in the second half of the year if the U.S. Federal Reserve looks like it will boost interest rates and if the oil rally loses steam.

The S&P/TSX composite index finished the month at 13,951, for a gain of 457 points, or 3.4 per cent, for the month.

On U.S markets, the Dow Jones industrial average shed 57.12 points, closing at 17,773.64. The benchmark index was ahead about 88 points for the month.

The broader S&P 500 index dipped 10.5 points to finish at 2,065.30, down 10.51 points on Friday.