For travellers to the States, when trying to get gas at a service station, and the pump asks for your zip code, and you are frustrated with having to go in and pay cash or leave your credit card at the counter, the following works with a Visa credit card and probably will with others.
Take your postal code, delete the letters, use the numbers only and add two zeros to the end and enter it as a 5 digit zip code.
Example: Our Postal code T5A 4J3, converts to 54300. Works everywhere I tried it. You might want to pass this on to anyone going south. (Most useful in California, Arizona and New Mexico.)
I thank the gas attendant at a Safeway gas station in Casa Grande, AZ for this info.