@salahuddin99,
Pl.check the following things to improve the gas mileage,
1 - Adjustment of gas from power T.
2 - Air filter for blockage.
3 - Improper fitment of venturi on carburetor.
4 - slippage of clutch disc.
5 - Check all the four wheels for free movement.
6 - Spark plugs,plug wires and distributor cap.