Depending on the year it varies very much. You have some of the older saabs that were strictly diesel.
A lot of the newer ones run on premium fuel only.
I have a Saab 9-3 Aero sedan. It is a 2005 model. It is a really great car. It has a lot of power and drives well. I haven't had any problems so far. The only downside to this car is the cost of maintenance. Parts and labor for this car are high.
The Saab 9-3 is a great car if you like a sporty vehicle and you also have a family. It gets great mileage and also has great handling if you live in a state where the weather can be bad in winter. They are front wheel drive which is also a great feature.