This is normally a sign of a vacuum leak. Check your dip stick for a solid seal. Also, does the Holden Cruze have a PCV valve? If so it may be leaking. I know http://www.cruzetalk.com/forum/34-gen1-1-4l-turbo/175793-cruze-1-4l-gen1-pcv-system-explained.html is for the North American 1.4T engine but it will be similar for all the Ecotec engines used in the 1st Generation Cruze.