Astra Crankcase Ventilation Issue

I had similar symptoms on my Astra. Any rough idling or whistling noises? It could be a ventilation issue, like you said. Is the smoke blue-ish?

Thanks for the quick reply. No rough idling but I did notice a faint whistling sound. The smoke is definitely not blue, more like greyish, do you think it's still the ventilation?

Greyish smoke aligns more with ventilation problems. Considering the whistling and the symptoms, it's very likely the crankcase ventilation. Best to get it checked by a workshop to be sure. Could damage the engine if left unattended.

Took it to a workshop, and you were spot on. Crankcase ventilation valve was indeed the culprit. Repair cost around 360€. Thanks for the help!