The BMW 645 has a powerful engine. It's not a full sports car, but it is a luxury vehicle. As such, it's important to maintain it properly. Not checking the oil or replacing the filter are two of the car maintenance mistakes that owners often make, despite this process being relatively simple. If you are too nervous to do the servicing yourself, have a mechanic do it. Either way, it should be done at least every 7,500 miles. The BMW 645 uses an internal oil filter.
Raise the car with a jack and secure it on jack stands. Locate the oil drain plug and remove it with an 8mm hex wrench. On the BMW 645, the oil plug is located under the car in a plastic belly pan accessed through a small trapdoor. Loosening the small drain plug bolt may be difficult, especially if the last time the oil plug was inserted it was done by a mechanic. If the threads are stripped, you will need to use a repair kit. Drain the oil into a deep pan.
Remove the car's oil filter. On a BMW 645, the oil filter cover is located in the same area as the drain plug. Use a 24mm socket to remove the oil filter cover then take out and discard the old oil filter.
Apply a thin layer of oil to the inside of the new filter. Install the filter by screwing it in manually then use the socket to give the filter an extra turn to tighten it. Replace the plug and fill your BMW's tank with 8.5 quarts of oil.
Lower the car off the jack stands with the jack.
Check the oil in your vehicle at every fill up. It's important to catch any oil leaks early on to avoid potential engine damage.