Why is my Audi A6's engine making a knocking noise?

I recently purchased a used Audi A6 and have noticed a knocking noise coming from the engine. What could be causing this and how can I fix it?

One possible cause for the knocking noise could be low oil levels in your engine. It's important to regularly check and top off your oil to ensure proper engine functioning.

Another possibility is that there is a problem with your spark plugs. It's recommended to have them checked and replaced if necessary to fix the knocking noise.

You may also want to have your mechanic check for any loose or worn out components in the engine, such as the timing belt or bearings, as these can also cause a knocking noise.