Hello,
Although a one time off the mileage can be achieved based on driving on highway at controlled speed of 80 Kmph
But on month on month - Looks unreasonable on real life day to day drive conditions
Pls note that General Motors has shut down its operations in Indian Market and the resale value of Chevy Cars has depreciated significantly
You have to consider same before making a purchase call
In terms of Chevy Spark Maintenance cost - refer
Chevy Spark Service Cost
Should help !!