The recommended engine oil for your 2007 Chevrolet Impala is the one which meets [GM Standard GM6094M] (https://pangea.stanford.edu/~schmitt/car/gm_approved_engine_oils.pdf) and displays the American Petroleum Institute Certified for Gasoline Engines starburst symbol.
GM Goodwrench® oil meets all the requirements for your vehicle.
The best viscosity for your vehicle’s engine is SAE 5W-30. These numbers on an oil container show its viscosity, or thickness.
If you are in an area of extreme cold, where the temperature falls below−20°F (−29°C), it is recommended that you use either an SAE 5W-30 synthetic oil or an SAE 0W-30 oil. Both will provide easier cold starting and better protection for the engine at extremely low temperatures.
Do NOT use other viscosity oils such as SAE 20W-50.
For more info, see this pdf version of 2007 Chevrolet Impala Owner Manual.
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