Which petrol station bothers having a website? All of the chains do it centrally and independent operators aren't going to be to bothered about the internet as a way of attracting customers, it's a cutthroat industry and those few thousand for a domain aren't worth it.
Think of other services. Car washes, detailing etc. That might be a better option, otherwise put up a google maps site listing service stations everywhere and what they sell, particularly good idea would be for ethanol fuels which are hard to find and becoming increasingly popular amongst consumers, they actually NEED to find out where they can fillup before they leave home.