SAAB 900 II TURBO: CONSUMPTION = 20 LISTS IN THE CITY

Hello! For 6 months I have been driving a Saab II 900 Turbo Cabrio automatic, Bj 1996. The good one drives like a bee, however, is soaking like a Kosake. At short distance (city, cold type, 10 minutes to work) 19-20 LITER SUPER takes. Is that normal? I know that gasolineers consume the first 10 minutes much more, which blows up here but limits. My old 70-80s gasoline Mercedes “only” consumed 14 liters, so 6 less than the Saab and were 15-20 years older… Facts: 1. 19-20 liters consumption i.e. city, after longer city trips not to get under 16.5 (I am also no raser) 2. 90 KM/h= 8 liters 3. 130 KM/h = 12 liters Is very much, right? Second thing: a month ago a lot smoked out of the exhaust (white smoke). Driven to the workshop udn suddenly stopped. For 3 weeks is again quiet. I.d. workshop could only confirm that a lot of oil can be seen in the exhaust, but the car suddenly stopped that day. Please H Help! Greetings