My Lanos Daewoo 1997 automatic model is consuming about 6 kilometer per 1 liter which is too much compared to average of 10 kilometer per liter How can I go about remedying this problem

New plugs and air filter ,is my first solution but as its a auto then it could be the gearbox slipping which would be caused by the front clutch in the box worn ,also the autochoke could be stuck on causing excesive fuel consumption ,in the uk in the old days we had lots of mechanics stories of women pulling the manual choke out to hang the handbag on ,or american tourists driving in first gear as they didnt know how to change gear .,Or the old man with reumatism driving with his foot on the clutch .Try the air filter first