My colleague had bought a Belta not Platz after selling Se Saloon. I had forget. I have updated my comment. The fuel economy of the car is good.
Although, if you want a good economy, low maintenance car with a pleasurable drive and super Ac performance, I suggest you should go for Altis. Its fuel economy is excellent as per reviews of fellow PWelers.
Also, I agree with your comment above that big body cars ie sedans with 1300cc or less seem to be underpowered. The same is true for Belta, City, and Glis. Once you ride a powerful 1600 or 1800 cc car you will know what you are missing.