I've been using Mobil 1 15W-50 in my 1.8Tqm, switching to 10W-30 for the winter here in Boston. Last night at the auto store I saw that Mobil 1 has replaced its whole line with the new trisynthetics. There's still a 15W-50, but the 10W-30 seems to have disappeared. There's a 5W-30 and a 0W-30 on the shelf. What's your advice? Switch to 5W-30, or stay with 15W-50 year-round?

Poethius

Same line, different marketing. Audi advises 5w30 up to 95 F (in the manual). That is what I use. It spools up discernably faster than 20w50 Mobil 1.