I bought a new i20 car in November 2020 but my car is giving a very low mileage of about 9 to 16 kmpl on the highway, what is the reason?

That mileage does not automatically mean there is a fault, because a 2020 real-world fuel economy of the i20 can vary a lot depending on engine type, speed, traffic and driving style. Common reasons are a new-engine running-in period, under-inflated tyres, frequent hard acceleration, heavy AC use, s