You will want to fill up the gas tank today before a significant increase at the pumps in Ottawa on Friday. Canadians for Affordable Energy president Dan McTeague says gas prices will increase seven cents a litre tomorrow at stations in Ottawa and across Ontario. In Ottawa, the average price of gas will be 185.9 cents a litre on Friday, according to McTeague. Gas prices dropped two cents a litre in Ottawa on Thursday to an average of 178.9 cents a litre. Diesel prices increased six cents a litre on Thursday, and McTeague says diesel prices will jump another three cents a litre on Friday to 259.9 cents a litre in Ottawa.