FAIR LAWN - Experts say drivers should be aware of how the heat affects gasoline as they fill up at the pumps this summer.

William Paterson University chemistry professor David Snyder says a gallon of gas in in the summer has slightly less mass than in the winter. The higher the temperature rises, the more gasoline can expand. Since gas is sold by volume, that means customers may be getting short-changed.

The fuel in underground storage tanks should be sold to consumers at around 60 degrees. But at a temperature of 75 degrees, drivers could lose a quart of fuel on a 25-gallon fill-up.

While there have been efforts in other states to govern the temperature at which gasoline is sold to customers, there are no such laws in New Jersey.

At the wholesale level, there are monitors which adjust the cost to account for the fuel's temperature. But at the retail level, there is no such adjustment, officials say.

The good news, experts say, is that car engines run more efficiently during the summer, which can offset the cost of paying for fuel you may not be getting.

The hot fuel issue has sparked lawsuits in several states, where six major oil companies reportedly agreed to a $20 million settlement.

One company, Valero, decided to not pay a settlement, but now posts the actual temperature of the motor fuel at its stations' underground storage tanks in 26 states.