Car: Audi A4 1.8 TFSI 170hp 2013 Sorry to be a bit of a noob but when it comes to engine oil I'm a bit confused. My Audi manual says that I should used VW 504 00 for (flexible) service or 502 00 for (fixed) service. 1) Now it doesn't specify if I should use 5w30 or 5w40 (according to Castrol search function)? 2) What's the difference between a flexible and fixed service? If I just wanted to top up the engine oil, which oil do I use? I checked my service bits of paper and it doesn't say what was put in.