Complex sentence: The third letter is generally used to specify the transmission type, although it can also be used to describe how many wheels drive the vehicle, and the fourth letter describes the fuel type and whether the vehicle has air conditioning or not.
Split into simpler sentences: The third letter is generally used to specify the transmission type, although it can also be used to describe how many wheels drive the vehicle. And lastly, the fourth letter describes the fuel type and whether the vehicle has Air Conditioning or not.