3.5-liter V6 Engine

• The standard engine for the Chevy Impala is a 3.5-liter V6 paired with a four-speed-automatic transmission. This engine is rated at 211 horsepower and 216 ft.-lb. of torque. Maximum towing capacity is 1,000 lb. This model gets 18 mpg in the city and 29 mpg on the highway, according to AOL Autos.
  
  

3.9-liter V6 Engine

• The top-of-the-line Chevy Impala LTZ is powered by a 3.9-liter V6 engine paired with a four-speed-automatic transmission. This engine is rated at 230 horsepower and provides 235 ft.-lb. of torque. The towing capacity for the LTZ is 1,000 lb. The EPA rates this model at 17 mpg in the city and 27 mpg on the highway.
  
  

Impala SS

• Up through 2009, a Chevy Impala SS model is offered, powered by a 5.3-liter V8 engine paired with a four-speed automatic transmission. The Impala SS engine is rated at 303 horsepower and 323 ft.-lb. of torque. Gas mileage is rated at 16 mpg in the city and 24 mpg on the highway, but unlike the V6 models, this engine requires premium unleaded gasoline.