The interior space of the Eco Up! doesn't suffer in the CNG version as the three tanks are in the subfloor. Two are for the CNG, and the other acts as a backup and contains gasoline (for when you go where there are no CNG stations). This gives the car a range of 380 km (236 miles) with just the natural gas; the gasoline in the reserve gasoline tank adds another 220 km (137 miles) of driving range. So, a total of up to 600 km (373 miles) can be covered with a single fill of the tanks.