[THE MORE YOU KNOW WITH ANTAWIRYA]
It is true that changing your air filter will increase your fuel efficiency. Dirty air filter will block the clean air entering the combustion chamber while the engine needs to receive air intake. This will make the engine to work harder so there will be more fuel to be wasted.
With clean air filter, engine will easily take the clean air into the engine so there will be no additional work done by the engine. Therefore, changing your air filter regularly will increase the engine performance and the fuel mileage of the vehicle.