Oil like solid minerals such as concrete do expand with rising temperatures but this article brings this to the point of paranoia with your gas station. It's assuming the the temperature in an underground tanks can reach high temperatures and thus expand greatly, costing you personally lots of money every year.

Well for one a protected underground tank for gas doesn't greatly cary temperature throughout the year. Even in a place like New England with cold winters and recent hot summers doesn't affect the temperature more than a few feet underground. Think of the partially buried homes some people use, they save people money on heating beacause they are partially underground which acts as an insulator. And during the summer, the buried homes are cooler inside because they are protected from the sun. A gas tank at least say 5-6 feet under our feet would not see that great change in temp around the year. The only time to worry is when they add more gas perhaps, the temperature from the truck stored gas being less protected.