Many of the differences between the LT and the Premier trims can be found on the exterior of the vehicle. While the Premier does boast a handful of internal features and safety add-ons, it is on the outside where most of the changes are experienced.
Wheels on the LT and Premier
First, there is the wheel size. On the LT, the only wheel size option is 18-inches. It comes standard with painted alloy wheels, although 5-split spoke machined-face with painted pockets aluminum wheels are available if that's the look you're going for. On the Premier, the standard wheel size is 19-inches, and the wheels are aluminum. You can upgrade to 20-inch aluminum wheels if you'd like (neither the 19 or 20-inch wheels are available on the LT model).
Tires on Both Trims
With both trims, they do come with a spare tire. Not all auto manufacturers include a spare tire any longer. In an attempt to save space within the vehicle and to improve the cargo storage room, several manufacturers are doing away with the spare and instead include a "tire repair kit." If you have ever experienced a flat tire, you know more often than not, the tire repair kit is all but useless. Unless the flat came from a nail puncture or something small and obvious, there isn't anything you can do.
Sometimes the flat comes from a pothole or something larger while driving, which can easily shred the tire. A tire repair kit is not going to do anything for this. It's a very small feature with regards to the rest of the vehicle, but whenever shopping around for a new car, truck, or SUV, always look to see if it includes a spare.
On the LT, the 2020 Chevy Impala comes with halogen headlamps. On the Premier, the sedan uses high-intensity discharge (HID) headlamps. The Premier also offers dual-exhaust tips instead of the single exhaust. This can help the airflow of the vehicle, allowing the exhaust to exit the car easier than what you find on the LT package.