Do you need to change the transmission oil for your MG dual-clutch transmission? Here are some reasons why it's important to do so:

1. It can cause damage to the transmission's shifting control mechanism.

2. It can cause abnormal wear on the gears and clutch plates within the transmission.

3. It can affect the normal operation of the transmission, leading to damage to the transmission body.

The replacement cycle for transmission oil varies by model. Here are the recommended replacement cycles:

Manual transmission: Manual transmission oil is generally recommended to be replaced every three years or after 100,000 km of driving.

Automatic transmission: Automatic transmission oil is generally recommended to be replaced every two years or after 40,000 km of driving.

CVT transmission: CVT transmission oil is generally recommended to be replaced every two years or after 60,000 km of driving.

The signs that indicate it's time to change transmission oil include:车身抖动, 换挡顿挫；仪表盘出现变速箱高温警告；汽车熄火；出现异响。

Here are the methods for changing transmission oil:

1. Release the oil by unscrewing the oil plug at the bottom of the transmission and then add new oil.

2. Remove the transmission oil pan and let the oil flow out, then add new oil. This method is more thorough and removes any impurities from the bottom of the transmission.

3. Use a smart transmission oil changer to filter and wash the oil and remove any dirt or debris.

It's important to change transmission oil regularly to keep your vehicle running smoothly and prevent damage to the transmission. Follow the recommended replacement cycles and be aware of the signs that indicate it's time to change the oil.