One thing to keep in mind that a smaller engine does not necessarily gives you better mileage. A smaller engine, just to keep up with the traffic, needs to be driven harder than a bigger engine. Thats why it could consume just about as much fuel as a bigger engine---the smaller engine is always working harder and is at a higher RPM at all the time. The fact that the 1.5 City gives the same economy as the 1.2 City is a clear example of this (The VTec in the 1.5 helps somewhat too).
I remember that I had my 1.2L (1193cc) 1989 Civic, which used to give me 10km/L in city with AC. This was compared to my brother's 1985 1.6L Accord, which also gave him 10! Both cars was carb.