A failure with the same catalytic cracker last summer resulted in as many as 90 Petro-Canada and independent stations in B.C. and Alberta running dry.
Seetal said on Monday that 24 of Petro-Canada's 159 stations in Alberta were empty.
The company has been shipping fuel to Alberta from its Montreal refinery and will be temporarily rationing fuel, she added.
Imperial Oil's plant, which processes 187,000 barrels a day, is also returning to full capacity after a shutdown and restart that took several days, said a spokesman.
Imperial did not disclose how many of its stations had run out of gas.