Far too many topics about what oil to use lately so here's a quick summary
The recommended oil for the 1.8T engines depends from dealer to dealer but it is always 5w40 or 10w40.
5w - this is the thickness of the oil at 0degrees. (W means Winter) The lower the number, the thinner the oil at cold startup. So this means through the Summer months 10w40 and 5w40 will perform the same. It's only when temperatures drop below 10degrees do things start changing.
40 - This is the thickness of the oil at normal running temperature.
Here's a quick comparison of the different grades of oil
Grade................0degC............10degC...... .........40degC...............100degC
0w-40...............665cst.............354cst........ ........82cst.................14cst
5w-40...............
842cst............
430cst.................
91cst.................
14cst 10w-40.............
874cst.............
440cst .................
91cst................
14cst 15w-40............1260cst.............595cst........... .....107cst...............14cst
As you can see they perform relatively the same at 10, 40 and 100degrees. It's the lower temperature that's the difference.
So in summary, what oil you put in is up to you. If you put 5w40 in the only difference between 10w40 is the thickness at start up temperature. I run 10w40 in mine and have never had a problem, others have run 5w40 and have never had a problem either. Don't get hung up on it too much
