A USA TODAY survey of eight car rental companies found prices of $7.99, or $8, a gallon at 10 airports surveyed. The prices were levied upon renters who return a car without a full tank of gas or don’t prepay for a full tank at the car rental company’s set price. The biggest rental car companies charge the most when customers don’t refuel a vehicle or agree to the prepay option.These high charges became controversial in Maryland last week when the state’s attorney general, Douglas Gansler, announced that rental car companies operating in the state had agreed to lower their gas prices after the state threatened to fine or sue them.Source: USA TODAY; find full article and survey chart here>>.