Every 12 months.
Proper spark plug operation is essential for efficient engine operation.
Execution order
1. Loosen the mounting screws and remove the casing from the valve cover.
2. Mark the high tension wires and disconnect them from the spark plugs.
3. Clean the area around the spark plugs and remove the spark plugs.
4. Negative battery cable and engine ground cable.
5. Measure the spark plug gap using a feeler gauge or special tool.
6. Adjust it by bending the tip.
7. Reinstall the spark plugs. To make installing the spark plugs easier, slide a short piece of tubing over the spark plug. This will act as a universal joint and prevent damage to the threads.
[Information obtained from this resource AudiManual.ru]