What oil do you use for Subaru impreza?

I started to use Mobil 1 (as I have done with other performance cars), and found it promptly knackered several parts in the engine as it was too thin!

I've now reverted to Shell Helix....

Essentially, it depends on where you are in the world, ambient temperatures, driving style etc etc. But you should be looking at a very good synthetic or semi-synthetic oil, I actually prefer semi-synthetics due to casters lubrication properties and my driving style.