In order to reduce harmful emissions to the atmosphere oil vapours are drawn into the intake system by controlled engine vacuum levels and are subsequently burned during the normal combustion process. In your case excessive amounts of oil in largely liquid form are finding their way to the air intake. Possible reasons for this are:
1. Over time the pipe work between the engine crank case and the air intake system becomes clogged causing restrictions which lead to excessive vacuum build up. This causes excessive amounts of oil to be drawn into the air intake. A good cleaning should help.
2. Although the mileage is not excessive for a modern engine depending on lots of criteria i.e how the vehicle has been driven, quality of oil used, how often the oil has been changed etc the cause of the problem may be due to excessive wear e.g. piston rings, cylinder walls, valve guides etc. A compression test will show whether this is the cause of the oil consumption problem.
Dann, September 2007
