So imagine my surprise when today I learned after this happened to me, the girl behind the glass handed me a piece of paper with a number on it, after asking me what my postal code was. She then told me after it worked, that this will work anywhere in America! So I asked her what the trick was and it is quite simple.
What you do is you take the numbers from your postal code and then add two zeros after that.
So for example if your postal code is A1A 2R0 then the number you will need to punch in to the gas pump when prompted for 'zip code' would be 12000.
Another example C3x 2R7 would be 32700.
Now you can truly feel right at home and not like a bloody tourist!