Is it necessary to use Armsoil 5-40Euro synthetic in my '02 Jetta wagon? Is there another alternative that's just as effective, but much cheaper? Thank you!

DO you mean amsoil? I would reccomend 5w40 castrol or mobile1 synthetic on 1.9L diesel, 1.8T, and vr6 engines. The 2.0L really doesnt matter what oil you use.