Other Fuel System Tank Filling/charging problems of the 2017 Chevrolet Malibu

Engine light on continually and never went off; I drove to dealer who said the gas cap area of fuel line was leaking; needs to be replaced they said and tried to order it from gm but they do not have the part; they ordered the part and cannot tell me when it is coming. They could not advise me on the safety of this condition. I know someone who had a similar problem with their model car. Can I drive this or should the dealer give me a loaner? I am still under the 3 year bumper to bumper warranty. We have always had problems filling the car and it is never completely full. We have brought it to dealer several times about this with no advise. They did recalibrate one time. They said it was an issue with the dash board reporting less gas than is in the tank. Please let me know about this as we continue to drive the car.