What kind of gas I can put in the tank? Premium or diesel?

I'm sorry I don't know what grade of fuel to use but all reserch on the web shows this is a gasoline engine that gets an average of 22 MPG City and 31 MPG Highway.

Diesel??? No! The Saab 9-5 was spec'd for premium, at least 90 octane on the US scale. But I've run 87 in it without any noticeable effects, except in summer, when it will ping on start up. In summer I sometimes use mid-grade or add octane booster, just because the stations are charging so much for premium these days (used to be 5-10 cents per grade, now often 20 cents or more).

premium gas only if you use diesel you will destroy your car.