@Aviral singh it is normal FE, but you could get better FE. You should test it on a long strip of highway journey where on cruising in 5th and maintaining 90-100-110 you should get 20+ of FE easily. The black deposits are normal but smoke could be because of bad fuel, wrong gearing with more over acceleration. The engine should feel stress free in every gear, over or under-accelerating will cause engine stress and some inefficient fuel burning. The FE will improve in time very soon as engine frees up. Don't worry if it does not immediately. Make sure you stick to one fuel brand and reputed fuel bunks.