What fuel do you think the next generation of engines will use?

Vegetable oil I suppose. In Brazil and other countries, they have already started using it.

In next generation i think hydrogen fuel may be use

I do not really know since we have made all the fuel we can think of right now. But, we'll see what else could be created.

i think compressed natural gas will be the alternative in next generation.in some part of world people are fixing a gas bottle in the vehicals,there are gas stations in different areas of cities they can feel the gas when it is axausted in the bottle.the charge of gas is less than half of petrol or diesel.