Well guys,leave the diesel and coming to petrol.
As per the latest data of a drive of we guys,its the Honda City which can deliver the FE even better than an Alto in the real world driving.
How I came to this hard-to-digest conclusion?
We people made a recent trip to a place about 60 kms away from my place and the cars were a Honda City and an Alto LXi(the one I was using as a replacement for Corolla).Both the cars were driven sedately at about 100 kph on the highway.At the end of the trip when we calculated the FE then we found out that the Alto delivered about 18.6 kpl while the City delivered about 19 kpl on the same road and same speed.
In other words,these hatches give good FE only till you drive them at the speeds of 60-70 but city gives good FE even if you drive it at 100 kph and with varying speeds.
So this way City is more fuel efficient than most of the hatches too.