He hasn't got the car la.. looking only..
Use 5w-40 engine oil la. 5w-30 if too thin for the engine, hence evaporate lor. It's a very efficient engine. 2.5L NA pushing 218hp, same as the 3.0L N53B30. The N52B25 runs hot, a little oil loss due to evaporation is just a price to pay for that kind of horsepower. If you don't need the extra horse power (who doesn't), you can always look for the older model E60 that don't have push start button, runs on M54B25, old school tech..
2003-2005 M54B25 - 2,5 L I6- 184 hp, 1,565kg, Aluminum block, 0.1176hp/kg
2005-2007 N52B25 - 2,5 L I6- 218 hp, 1,550kg, Magnesium block, 0.1406hp/kg, 20% more hp/kg compared to M54B25
2007-2010 N53B30 - 3,0 L I6- 218 hp, 1,585kg, Magnesium block, 0.1375hp/kg, 2% more hp/kg compared to N53B30, no valvetronic motor because blocking the high pressure injector for improved smaller carbon footprint (I think) ..