When to use D2 in an automatic car?

D2 in an automatic car is typically used for driving in hilly or mountainous terrain, as it allows the vehicle to maintain a lower gear for better power and control when going uphill or downhill. It can also be beneficial in situations requiring more engine braking, such as descending steep slopes, to help prevent the brakes from overheating. Additionally, using D2 can enhance acceleration in certain conditions without shifting to a higher gear too quickly.