well maintained santro ff cng give 220km in 42 liter cylinder(yes kuch santro 80-85 km b karti hen wo b chalai hen mainy avg santro 150-200 tak karti hen), even once on motorway i travel 257 km in on filling 5 members with full hard foot (110-140 kmph), 165/65/13R n 35 tyre pressure, auto fan, now you calculate the mileage with 102 liter cylinder