But CNG and gasoline engines go together. Riding in several of my Italian friend's cars, they could run on gasoline or CNG. I remember one's Ford Fiesta had a switch by the gear shifter that switched between fuels. CNG was in 2 glass wound high pressure tanks behind the rear seat. The original gasoline tank had been replaced by a 20 liter tank. He always ran CNG in Italy but stations aren't prevalent in the rest of Europe therefore the gasoline capability. Switching was seamless - I tried switching fuels while he was driving under various conditions and I couldn't notice any difference. Like most Italians he drove even wilder than I do so I got to try the switchover under full throttle acceleration many times and no difference. The difference came at the station where it cost him less than half per kilometer to use CNG or methane over gasoline.not sure how much of that was tax incentive and how much was actual cost. Tax incentives vary greatly by country in Europe. I owned a diesel because in France diesel was significantly lower in price than diesel. Cross over into Switzerland and diesel owners ay the penalty.