Depending on your cliimate 5w-30 for colder climates or 10w 30 for warmer climates. As for brand I personally prefer Valvoline but any SAE appreoved motor oil will work.
Dexcool
5w-30 is reccomended for the 3.5l v6.
5W-30 is most recommended for a 2006 Chevy Impalawith a 3.5 liter motor. 5W-30 is most recommended for a 2006 Chevy Impala with a 3.5 liter motor.
If it is slipping in gear or any out of the ordinary rough shifting.....
Dexron-VI Automatic Transmission Fluid(ATF)...
The 2006 Chevrolet Impala has overhead valves (OHV).
gm 4t65e
The Orange Dexcool
Mine had a 350 turbo in it.
Ramone is a 1959 Chevy Impala
Dexcool
AC/Delco