gladiator, the stock tyres HAVE to be changed. i believe they're 13" 165...very very poor road grip...i have installed my exi's 14" 185 tyres in it, the road grip is much better but nothing like the 15" 195 that i had on it earlier. I would like to emphasize again that people wanting maximum fuel economy and comfort should not exceed 14" ( im talking from personal experience, after going back to 14" my citys ride has significantly improved besides improvement in petrol average, hence there shall be no need of CNG)