Best but in price not in efficiency

Car is good power is excellent every thing is ok. No douggt car is best but millage in petrol varient 12 to 15.1 km/l maxmimum that I absorb both hightway and off road. Today other car gives more then 20 so why kuv not, car is good but in disel vareint and the wheel tyre is 14. It should be replaced to 15 because car is big so why tyre could not. Many thing that we absorb after 5 months from the date of purchase.