For a brand new 1.3 motor, I would sugguest Mobile1 15w50. It's a full synthetic, so it's a little pricey but worth it! In larger motors I run 20w50, and I've never had a problem. When I was working for Mercedes, we used ONLY mobile1 oils. Here's a link for you to check out though. It should answer or lead to answers for any questions you may have.
Mobil 1 15W-50
