Hi. I've got an 56 plate S3 and I've noticed at idle it rattles a little. Only when at operating temperature, its fine when cold. I've read and searched the forum and found loads of topics relating to the TFSI engine sounding like a diesel which I can accept. The only reason I'm questioning my engine is I've drove another S3 the other day it was so smooth and had no rattle at all. Both cars have similar mileage (mine is 45,000 and the other one is 39,000). So the question is, Can I swap the oil from 5w30 to 5w40 to try and keep it quiet once warm?