V70 LPG – extremely high consumption

Hello together, as a Volvo newcomer I have a question about the consumption. My “new” 2.5, 144hp V70 LPG approves itself with mainly urban traffic 15 liters. I consider this despite automatic transmission and just quite many short distances for extremely high, or am I mistaken? The old Swede is year 98 and has 180,000km down. The gas system is from Vialle with a 100 liter tank, was built in in Holland and otherwise runs perfectly. I am otherwise very satisfied, only with such a high Verbra I didn’t count for it. I ride it very gently, usually let the automatic switch on at under 3000 tours. He is a miracle of acceleration, but God doesn’t know, but I don’t want to drive the consumption even higher. Since I don’t know any comparison values and otherwise only drive Audi A6 Avant V6 diesel, I would be grateful for your opinions. Greetings, Michael