define green! In some circles, green means no emissions, which means no energy use, therefore, the answer is NONE. On the other end of the spectrum where green means lower emissions than was the norm 10 years ago, there are a few.
Low sulphur diesels, a new invention that has helped. All diesel engines made today in the S must use it. Addition of small amounts of biodiesel help reduce emissions. Smaller light weight cars with enginesundere 1.8 literusingg gasoline would be in thatcategoryy too.
Toward the bottom of the list in reduction is electric cars since they use energy from coal. Oh, some will say that their electricity comes from hydro, its a lie, we all lie on a grid and we all share the power from it, even those that pay extra for green power cannot physically trace that electron to a windmill,
Ethanol is toxic to humans and animals. Ethanol produces more CO2 per mile driven than gasoline. Ethanol has a higher volitility so in order to use it without it eveaporating away overnight, you must have a pressurrized fuel system, which vehicles post 1980 have, so there is little VOC escaping. But because we mix ethanol with gasoline, the ethanols high volitility makes the L/V ratio go toward a high vapour ration meaning more benezenes are released into the atmospher. Gasoline makers have countered benzene release from ethanol fuels and regular gasoline by converting benzene to cyclohexane.
Ethanol has a high octane rating, but not one manufacturer has built a car for sale in the US to take advantage of this. The only places where people take advantage is on race tracks, why you ask, because engines that take advantage cost twice as much.