Oil Function: Notes
WARNING: This page is about a different car, the 2008 Volkswagen R32. However, it is still accessible from the selected car via links, so may be relevant.
Oil does not just lubricate the transmission.
The oil also transports the finest differential abrasive parts in both filters, ensures the lubricating film does not wear off the differential tooth flanks and at the same time, it acts as a gear selector pressure medium to enable it to perform its functions.
It also seals the selector lever and helps the synchronizer rings when shifting gears. It conserves and transports warmth, minimizes noise.
To maintain this degree of performance, the filter on the transmission should be replaced during the oil maintenance service.