Had to put in a litre a few thousand miles ago.... Now on 18000 miles... 1st oil service on Tuesday (now 300 overdue - but the service rep said that up to 1000 was OK, when we were deciding on a date on which they could pick it up and drop it back.).
E90 320D has... Conventional dipstick (part of engine used to check the oil, NOT the driver!), Low oil warning, no temp gauge for either the engine or engine oil.