Oil passes to the admission multiple

Hello, in what anomalous situation the oil can go to the admission multiple in an Opel Vectra in 98, multiveralvular?

Some oil vapor in the intake is normal and comes from crankcase gas recirculation. You haven't told us if it's a diesel (turbocharged) or gasoline engine. If it's a turbocharged diesel, the excess oil in the intake could be due to wear on the turbocharger shaft. Excessive engine wear (cylinder-piston) can cause high pressure in the oil pan, leading to excessive oil blow-by and the release of all this vapor into the intake. Another cause could be a problem with the crankcase ventilation system (a PCV valve stuck open due to dirt).