good mileage of 30

Mileage I  fitted my micra with 165/80 R 14 swift tires. actual speed=sp speedometer speed x swift tyre circumference 1948/micra tyre circumference 1848=speed  x 1.05   actual mileage = tank mileage x 1.05 Best Features : my dci diesel gave only 26.8 kms mileage only , i was jealous over logan car owner for my less mileage.but now after 11000 kilometres same vehicle giving  30.04 mileage [ 15% city + 85 % highway] without ac 1800 rpm sharp. Micra consumed 15.48 litres of diesel for 465 kilometres .route full of potholes for 15 kilometres stretch karaikudi to coutrallam via madurai via madurai inside city traffic also with 1 st gear moving for 1 km, following container lorry for 5 kms in second gear 5 stops 5 reverse gears , parking with all these it gave 30.04 km mileage[ previously only 26.8 ] before 10000 kilometres. fourlane  above 32 km mileage