thanks for the help. you are right, that tyre change will affect the car efficiency.
but, i am also not happy with the general tyres(175/70/r13). please suggest any best company from dunlop/bridstore/yokhoma or any other based upon your experience. i am planning to install 185/65/r14 or 185/70/r14 tyre size. which size will have less impact on suspension/fuel economy, but resulting increase in height? otherwise i will keep the current size(175/70/r13), and might add "packing" in rear springs.
What you suggest and what tyre size you are using?
by the way, i got my car tunned. and now i am getting average of 140+ average on CNG(which was 110 before tuning) in city traffic. not sure economy on highway/motorway, as i still not drive car on motorway. i am very impressed with its cng/fuel economy.