Hello Mani,
If its a new car - personally i would not be very comfortable on LPG
- Firstly it will void any warranty on brand new car
- Power Loss in LPG Vehicle. You can surely expect loss of power - if you go with alternate fuel - cng/lpg
- LPG price is higher than CNG or Diesel and even average is not too great - There wont be any huge savings in LPG Fuel over the Petrol in running costs
- The car develops a kind of smell inside the cabin sometimes - think of it of a new car having even a slightest gas smell inside the cabin
Last - Even ignore all above - Had there been no impact of LPG on performance - do you think that manufacturer could have missed cashing on LPG in Swift (or even CNG)
When the savings are on lower side in running costs - it would not be advisable to go to alternate fuel at the very beginning when you buy this car.
My recommendation is - If you cant buy a diesel version and your running is high - go for CNG Cars . Some descent options been :-
Wagon R CNG, Hyundai I10 CNG
You can refer below for more info-
CNG and LPG Cars in India