I read on here that they go bad without warning and that they are cheap to buy and worth having a spare around since parts are hard to come by for these cars. If I was with a bunch of XF's I wouldn't worry about it but with a bunch of Subarus I'm screwed.

There is a post in this section about a place online and how to install it and all that stuff. I spent about $50 for a sensor and a new oil filter and hopefully that will buy me some peace of mind.