I'm sorry but I'm in Indonesia and I'm not used in using miles/gallon, I'll use km/litre. The daily consumption of my m/t 2004 Aveo is around 9 to 11 kms/litres (approx 20,67 miles/gallon). It really depends on how deep you step on the gas pedal. Try to hold it under 2000rpm and it can be more efficient. But don't force to use high gear when you don't have enough power, you can lose gas for nothing. Just try to understand the characteristic of the road.