I purchased a Zen Lxi Petrol 2006 Feb model. I guess you would have read most reviews so I wil spare you the usual. Mine gives around 11 kmpl(with AC) BEFORE the first servicing (I expect this to go upto 14-16 after the first 3000 km.) Even though Alto and Zen have almost the same exterior dimensions Zen is much more spacious and comfortable for the pasengers at the expense of the dicky. Suspension is awesome and I feel much comfortable even on the Pimpri Chinchwad roads. The zen is quite reliable and I need not say much on that front. I also went on long distance drive on a highway as well as village roads and even after a few hundred km I did not feel exhausted.
Let me tell you a bit on the minus side. The gears are not that smooth but good nevertheless. The turning radius is quite high but with power steering you don’t feel much effort but you gotta be cautious. And while uproaching slightly higher bumps on road you better approach it diagonally which I could easily clear with my earlier car Maruti 800.
However the reliability of the current zen is time tested. And since Maruti wants to offload the stock you will get great deals from your Maurti dealer
Now I would advise you to buy this current model before the new one comes out. The new one as per the rumors looks like a bug and has a hybrid look between WagonR and Matiz. Pathetic to look at and we do not know what lies beneath the hood as compared to today’s relatively sporty look and reliable machinery. However your guess is as good as mine on the new zen.
<update>Mileage of Zen
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After my second servicing I am getting an average of 18.5 kmpl.
The mileage measurement is by the method of full tank by sensor at a known petrol pump.
The petrol is HP plain petrol. Note that this same method showed about 13 kmpl before my servicing and I was pretty depressed about it.
The measuremnt is over a 110 km stretch which includes 54 km of city driving about 7 km of hill driving ( 2km of AC included) and the rest is highway drving at a speed of 60-80 kmph.