They're regular American gallons.
CD is using the EnerGuide mileage numbers measured by Canada's NRC, not the EPA mileage numbers. The EnerGuide measurement system seems to produce higher estimates, especially for highway driving. If you look at the "50 Litre Challenge" results, it's probably fair to say that the EnerGuide numbers are more accurate for real-world highway driving than the lower EPA numbers. For city driving, I think the EPA numbers tend to be more accurate.