vacation has just begun and you're making the drive to the mountains or to the beach or to some other place that you've been dreaming about for months. You're ready to go, but before you can go more than a few miles, you have to head for the nearest exit – it's already time to buy gas. With gasoline prices as volatile as they've been in recent years, this isn't likely to be your favorite part of the trip. There's even a chance that sticker shock at the pump may lead you to skip that evening's fancy dinner and stop for a fast-food meal instead. Unfortunately, in a world that depends on automobiles for basic transportation, pumping and purchasing gas is a necessary evil – for the moment, anyway. Article continues on page after next