It depends on what model year you are talking about. Most recent BMW's (post 2006) have an electronic oil check that you access by pressing a button on the dash. Therefore, there is no actual "dipstick" in the engine bay.
where is the oil dipstick on a bmw 320i petrol engine
5w-30
The oil on a BMW Z4 is changed by putting a oil drain pan under the engine, placing the vehicle on jack stands, and removing the oil drain plug. The oil is then allowed to drain, the plug re-installed, and the engine filled with oil.
The oil dipstick on a 1997 BMW 528i is located on the left side of the engine. It has a tube which connects to the engine block and directs the dipstick into the bottom of the oil pan.
5w-30
It's in your Owner's Manual.
The 2012 BMW Z4 has 16 valves.
The 2005 BMW Z4 has 24 valves.
The 2009 BMW Z4 has 24 valves.
The 2008 BMW Z4 has 24 valves.
The 2011 BMW Z4 has 24 valves.
The 2010 BMW Z4 has 24 valves.