Automatic transmissions make sure that the engine always runs in the ideal efficiency range. With increasing complexity of the transmission control by adding 5 to 9 gears, however, there is also an increase in the performance requirements of the transmission. This is reflected in the enormous thermal and mechanical load on the transmission oil. The effect: increased wear and thus increased requirement for maintenance. In case the transmission oil is not changed in time, the dirt and metal abrasion contained in it can cause costly mechanical damage in the shift box. Consequently, their manufacturers and also more and more vehicle builders are issuing recommendations for changing the transmission oil, depending on the mileage, and driving style. This is also valid for so-called "lifetime fillings". A complete exchange of the lubricant was not possible in the past. When changing the transmission oil, contamination of the fresh oil with the remaining used oil was inevitable. With Gear Tronic II, this problem is now a thing of the past. That is because the automatic transmission oil service unit enables an almost 100-percent fluid exchange without mixing fresh and used oil. Only in this way can the new oil develop its full performance.