What would be cheapest on gas to rent car malibu one week $100 with crusise control or drive my Impala no crui

It depends a great deal on where you are driving, city, country or a combination. Actually, if the driver is careul, these two cars should be very nearly equal if they have the same size and type of engine. Unless you are driving 1000 miles a week, the fuel savings will be insignificant with regards to repairs, tire wear, insurance coverage, and traffic situations.