It can be that the float level is set to high and that the fuel is then leaking by on the pistons resulting in the oil been poluted by petrol. that is if it is a carburator unit.
On fuel injection it happens when the injectors are dripping resulting in the same.
On both occasions it will effect the performance of the vehicle.
Roland, April 2009
If its an old corsa, and not fuel injection, it looks like the fuel pump diaphragm is leaking, allowing petrol into the sump. Are you sure its petrol?
