Chevrolet Aveo Engine Poor Mileage

I Have The Vehicle Listed Above With A 1.3 Diesel Engine. It Has High Fuel Consumption But Runs Normally. The Mechanic Said It Might Be The...

I Have A 08 Chevy Aveo And I Work 80 Miles Away From Home, The Car Is Supposed To Get 34 Miles To The Gallon, So I Drive To Work And Back...