Complex sentence: EF4 & EF7 engines use CNG as their main fuel and they can also use gasoline & EFD uses high quality diesel (at least Euro 4 diesel) fuel as its main fuel.
Split into simpler sentences: EF4 & EF7 engines use CNG as their main fuel and they can also use gasoline. It uses high quality diesel (Euro 4 Quality or better) fuel as its main fuel.