Not the right stuff to use I'm afraid, the 0w bit means it is too thin when cold, the 40 bit would probably be ok, 5w30/5w40 or as some Impreza owners tend to use, a 10w40/10w50 would probably be fine.

Here's what the numbers mean http://www.upmpg.com/tech_articles/motoroil_viscos...

Here's a link to recommend an oil for you car http://www.opieoils.co.uk/t-recommendations-car-or...

Hope that helps