@OP; its a great car to use on petrol, i have it and every one is shaky abt installation of CNG in it.
other wise on petrol its gr8 car, mine did 50K KM and it's 2008 model too
just afordability is an issue and for this is bought swift as a daily runner with installation of CNG.
heard there is no issue if installed all orignal stuff but even than i would not recommend to take such risk.
if you can afford petrol go for it, and if you cant than big NO