Either internal leaking or external leaking
External :
1. Check for stains on floor after parking overnight
2. Check for oil stains around engine bay area, oil filter area (most accessible and visible areas)
The oil stains should be yellowish-brown around the seal areas (aka where there is slight gap between 2 components
If your engine bay area is dirty, then the oil would be covered by black soot.
Usual cause: worn seals
Solution: go workshop and change the seals or watch youtube for DIY
Internal:
1. Start your engine after parking overnight, idle for 10min
2. Ram the accelerator (gear at P!!!) hard and have someone observe the exhaust. If lots of white smoke, then engine oil probably would have leaked inside.
Usual cause:
1.worn housing gasket (or whatever you call it, but need to open the engine to replace)
2.worn valve seals
3.worn pistons (?)
Solution: Go workshop to change the stuffs, but look around, a lot of workshop will tell you either TOP or FULL engine overhaul instead!
heard from somewhere that its very 'common' for valve seals to be worn for 3 series by the 5th year.
Good luck!
