The Globe and Mail has an interactive tool to calculate if it’s worthwhile driving a certain distance for cheaper gas. A lot of Canadians do this, especially on a trip down to the States. I’d probably never go down on purpose just to get gas. I’d likely fill up if I were going on a trip south. So I fill up once I cross the border and once before coming back home. Then getting gas would be worth it
A Google search of Blaine gas prices suggested that the Chevron near the border actually sells regular gas for $4.35 per gallon. I based the calculation on this $4.35 per gallon price which works out to about $1.15 per litre. The distance is from somewhere in Vancouver proper to the Chevron just across the border. The car chosen for this calculation was a Honda Fit.
What this calculator doesn’t take into account, though, is the time spent lining up at the border. My savings are probably eaten up in a long queue to cross the border. If you a Nexus card, then maybe the effect of the line up on the savings would be mitigated.
The only time I ever fill up across the border is if I am actually going to spend time in the States for a day or two. Otherwise, I don’t think it’s worth the trouble. I would only save less than $5. I might as well spend my time doing something locally.