If you like Civic but hate its mileage (Its wrong to hate either, what mileage can we expect from 1.8L engine?
), then you can try Honda City i-VTEC. I bought it recently and I love it. Mileage is around 12 - 14 city and +1 highway.
Hyundai Verna is also a good car but the design is lil out dated now.
Gas fitting for these premium cars doesn't make sense. You will lose performance, engine life and status of the car.
For long run and better mileage, go for diesel. Petrol is for those who have bundles in pockets.
In short run (like me), diesel or petrol doesn't make much difference. We won't get poor by using a petrol car.