I'm getting the bits and pieces for my service, and need to know what oil I should be running. I went to Halfords, they told me 5w30, went to Castrol - They said 5w40. Looked around the forum - ppls are running 10w30. What do these numbers mean and which one should I run?? I'm leaning toward the 5w40 by Castrol (as its a good make) I have a 1 litre 2ndfacelift coilpack if that's any help....I think, don't quote me on this, all the oils will actually be fine, the numbers have just got something to do with the temps I think....correct me if i'm wrong??