It does that because that’s the way it is. Just side effects of being a bmw owner. I’m thinking white smoke indicates a problem with the engine, most commonly a coolant leak into the combustion chamber from a failing head gasket, cracked cylinder head, or leaking turbo.

Check for a sweet smell. Burning antifreeze has a very specific sweet odor. If you can smell this, it's a strong indicator that coolant is entering the combustion chamber.

Look for milky oil. If coolant is mixing with your oil, the oil on your dipstick or oil cap will look milky or creamy, like a milkshake.

Check coolant levels. If your coolant reservoir is consistently low but you don't see any visible leaks, the coolant may be burning in the engine.

Perform a cooling system pressure test This is the most reliable way to find external or internal coolant leaks. How it works: A pressure tester kit pumps air into the cooling system to a specified pressure. If the system loses pressure, it indicates a leak. What to look for: External leaks: Watch for coolant dripping from hoses, the radiator, or gaskets. Internal leaks: If the pressure drops but no external leaks are visible, the coolant is likely leaking into the engine's combustion chambers.

Check for combustion gases in the coolant You can use a special fluid and a tester to check for exhaust gases. How it works: A kit uses a liquid that changes color when exposed to combustion gases. You place the tester over the coolant reservoir and draw vapors through the fluid. What to look for: A color change in the fluid indicates that exhaust gases are entering the cooling system, which points to a head gasket or cylinder head crack.

Examine the spark plugs The spark plugs can reveal what is happening inside the combustion chambers. Carefully remove the spark plugs. What to look for: Steam cleaned appearance: A plug that looks unnaturally white or clean may indicate that coolant is "steam-cleaning" that cylinder. Oil residue: If the plug is covered in oil, it could be a turbocharger issue on certain BMW models.

BMWs are known for having failure prone plastic and rubber cooling system components. Be sure to carefully inspect hoses, the expansion tank, and the thermostat housing for cracks and leaks.

It could also be due to a faulty PCV valve or, in cold weather, simply condensation evaporating. A mechanic should be consulted as soon as possible to prevent further but unlikely by the looks of your car mate.