Gasoline that is bought "hot," that is, at the hottest times of the day, costs the nation's motorists over $2 billion a year. When the temperature is up, stored gas expands. So customers get less for their money at when it is hot outside.

These days every bit helps because of the skyrocketing price of gasoline, so try to pump your gas later in the day or at night.

For real-time gas price information at stations in your area of the U.S., go to GasBuddy.com.