Ottawa motorists will want to fill up the gas tank today or wait until Saturday, as prices are set to rise and then fall heading into the weekend.

Canadians for Affordable Energy President Dan McTeague says gas prices will increase eight cents a litre in Ottawa on Friday, bringing gas prices to $1.749 a litre.

However, McTeague forecasts a seven cents a litre decrease on Saturday to 167.9 cents a litre. 

Gas prices dropped 20 cents a litre over a three-day period last week, with stations selling gasoline for 159.9 cents a litre on Saturday. Motorists saw a seven cents a litre increase in prices on Sunday.

McTeague told Newstalk 580 CFRA last week that motorists shouldn't expect the lower gas prices to last.

"The markets, I think, are overestimating the amount of demand drop we've seen in the United States and underestimating the severest supply shortage that we're having," McTeague said.

According to ottawagasprices.com, the average price of gasoline in Ottawa one year ago was $1.31 a litre.