LM,
The Series 2000, 0w-30 can be used to replace 5w-20/5w-30/10w-30 oils. I'd even recommend it in engines that come with 0w-40 or 5w-40 grades. Wear protection is at least as good as the Amsoil 10w-30, but with a few percent better fuel efficiency. I've run just about everything Amsoil makes in my Audi 100, and the 0w-30 generated the lowest oil temps and the highest fuel efficiency. Compared to the Amsoil 10w-30 I used to run, I consistently picked up about 3% in fuel efficiency.
There really is little call for a 10w-40 for most modern gas engine applications. Most of the Amsoil 10w-40 I sell is for diesel engine passenger cars and Japanese motorcycles.
If your SAAB is in good mechanical shape, the 0w-30 will work just fine ....
TooSlick