Other Fuel System Tank Mounting problems of the 2015 Hyundai Sonata

Since leasing the vechicle on August 1 I constantly complained about the gas mileage which hyandai indicated would be resolved on the following oil change. The oil change bearly effected the mileage efficiency which leads to the second issue when the gas guage shows below a quarter on the tank the cruise control does not work and is also affected in high mountain areas. When I explained these issues to hyandai they said they never heard of it and would sent to the company for further review in the meantime I have a car with the gas guage that does not show exact amounts from fill up to empty makes this car a safety risk that is totally unacceptable not to mention the car is running horrible which suggest other safety features are not working accurately. The dealers look over only suggested other underlying issues exist with this vehicle and is a clear safety hazard.