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Canadian Credit Cards

Many fuel dispensers in the USA (for sure in Hawaii, apparently elsewhere in the USA as well) accept the numbers-only from the postal code of a Canadian billing address followed by two zeros.

So, if your Canadian billing address is right beside Schwartz's Deli in Montreal where the postal code is H2W 1L2, you would enter '21200'. Where the '212' are the numbers from the postal code, and the '00' is padding to get to 5 digits.

Interestingly, if your billing address is in Head-Smashed-In Buffalo Jump, Alberta where the postal code is T0L 0Z0, you actually would enter '00000'.

Edit: I just tested this on January 23rd, 2014. It still works.

UK Credit Cards

I have a UK credit card and have had mixed results using my card at the pump. Sometimes no ZIP code is asked for and it works fine. Also, sometimes entering 00000 does work (I'm guessing because it's not subsequently using the ZIP code entered). In about 80% of cases, though (and it does seem to vary as to where in the US you are), I've had to go into the gas station - although they generally seem well equipped to handle the exception process (by which I mean, at that point it doesn't seem to matter that it's foreign - I just ask for X$ of gas and they charge it - the difference being refunded if it's unused).

German Credit Cards

I've had mixed results with German credit cards. Since we also have 5 digits ZIP codes, the match should be fairly easy. However, on some occasions it worked perfectly, while on others it didn't and I had to see the cashier. All in all, there doesn't seem to be any kind of rule or system - at least not to me.

Swedish Credit Cards

Swedish credit cards work fine. You can type in your Swedish zipcode (also 5 digit) but I honestly doubt the system checks for foreign cards.

I have UK and Italian credit cards. Italy also has 5 digit postal codes and I've sometimes been able to use the postal code at the pump with an Italian card.

I've also called my credit card company and asked if I could put a temporary address on a credit card so that I could have a zip code associated. In my case they said I would have to have that as my only address but could change it back later. In the end I decided not to do that, but might be worth asking if your credit card company can do it. Perhaps just put the address of the hotel you're staying at.

As other people have said, I've also had luck using just the digits of my UK postal code padded with zeroes. I've never been able to use all zeroes.

The mechanism that the gas station uses, is the credit card Address Verification Service. It's worth noting that there seem to be restrictions on this in various US states as noted in this cpn site:

There are some controversies and legal issues when requesting AVS
information. For example, in California and Massachusetts it may be
illegal to ask for ZIP code information, as this is seen as a privacy
violation.

This may explain why all zeroes are accepted in some places and not others.

AVS works differently with different card suppliers, so it may be possible that a Mastercard works with a foreign 5 digit postal code, or zero-padded postal code, whereas an Amex doesn't, or vice versa.

Australian credit cards

Australian credit cards don't seem to cause much of a problem here - I was able to use 90210 (which is always my go-to American zip code, probably like many!) on gas stations in both Florida and New York.

This was with an Australian Mastercard.

Swiss credit cards

Not tried yet at the pump.

At a Long Island Railroad ticket machine in New York City, the code was asked. I accidentally tapped the "Continue" button on the touchscreen witout typing any code, and it worked.

FYI The zip codes in Switzerland have 4 digits.