BMW automatic transmissions are sealed units that use a special oil to lubricate and create pressure. This automatically actuates components inside your transmission without the need of a clutch pedal or for you to manually shift gears. BMW automatic transmissions are sealed units (no dip stick) which have “lifetime” fluid. The lifetime fluid is generally good to get your BMW to 100,000 miles, but then will quickly break down after as the miles keep piling on your transmission. The fluid will break down and will actually start to prematurely wear components inside the transmission.
Your BMW’s transmission uses a special transmission oil and a filter just like your engine, but transmission oil change intervals can be much longer. BMW considers it “lifetime” fluid because by the time the fluid has degraded to the point it is causing transmission issues the car will be well out of warranty. When transmission fluid is new it bright red on GM supplied transmissions or gold on ZF supplied units and as they break down the fluids turns black. Finally you’ll start experiencing transmission issues such as slipping or bucking once either fluid is completely depleted. Since BMW didn’t install transmission oil dip sticks to easily inspect the fluid’s color, it more important to change it at appropriate intervals to prevent damage.
With 40,000 transmission oil and filter change intervals we have had customers with daily drivers who have racked up over a quarter million miles on the original transmissions. For customers who track their cars or drive more aggressively we recommend more frequent intervals. As for the added maintenance of transmission services, they are much more economical than suddenly getting a check engine light needing to replace the entire transmission.