Which oil weight should I use?

[fjg@ch.hp.com (Frederic Gittler)]

There has been much traffic on the net recently over synthetic oils. I have
been using Mobil 1 on all my automobiles since 1985, and has never had any
problems of engine wear or oil consumption. I will keep using it.

I am now trying to decide on what to use for my new S4. I am very tempted to
run Mobil 1 5W30 year round (even though the summers can get quite hot at
times here in the Boston area.) I have been using that same oil in my
Quantum Syncro, with no problems at all (120,000 miles now, still no oil
consumption.) The S4 Owner's Manual, furthermore, gives the same temperature
range for the "energy saving" 5W30, 5W40, 10W30, and 10W40.

Given my driving style (I do not "push" the car continuously), do I make a
mistake using the 5W30? Should I use 10W30 instead? The reason I edge for
the 5W30 is the better protection (I think) it provides in the first few
seconds after starting up the engine.

I welcome opinions and experiences from the readers of this list...
---
Frederic Gittler

'94 Audi S4 Quattro
'91 Toyota Previa LE All Trac
'86 Volkswagen Quantum Syncro