Continentals tyres do have good reviews.
However larger tyres are for heavier cars. If you keep 30 psi in bigger tyre then weight of Alto is quite light for them and the average would have definitely increased. With rising fuel price every other month the carmakers are now recomending 35 psi pressure for stock tyres. If the roads are good in your area you can give 35 psi a try and inshaAllah will get 25 km/l on factory fitted ones.