The Khyber/Swift 1000 were considered to be quite fuel economical cars back in 90s. These days mostly Cultus carby are also facing such fuel economy issues.
In case ur Khybers Carb is badly worn out or damaged then u might need Carb replacement other wise general rapairing with replacement carb kit shud get ur car's milage to 10+ within city or ~14 on highways or good carb rebuild job in presence of good Engine condition may further enhance the milage per liter.