When drivers hit the road for fun this summer, filling up at the gas station will be easier on the wallet. Compared to last year, fuel should cost more than a dollar less per gallon in the United States. It will likely be lower in Europe, too.

The wild trajectory of gas prices over the past 10 years can sometimes feel more stomach-churning than any amusement park ride. Factor in the differences among fuel types, states, and countries worldwide, and it's no wonder traveling consumers have questions. We answer a few here.

U.S. gas prices will average $2.45 a gallon this summer—a 31 percent drop from last year's $3.59 average, according to a forecast by the Energy Information Administration or EIA. In