When talking mileage, efficiency or greenness you have to establish what that in fact means, and then be able to compare the automobiles by a similar set of standards.

That is way easier to state than to do.

Diesels are the most efficient of the internal combustion engines in common use. That means you can get more work out of a smaller or equivalent sized displacement for longer and using less fuel, and the fuel requires less refining.

Mandates in U.S. law have also resulted in a large reduction in emissions of diesel generators. Like say more than 90%. Requires a small tank of urea that feeds post combustion gases but will work very well when it works.

Diesels still put out soot that goes into lungs permanently.

Many electric and hybrid vehicles have been recovering electric energy through braking for years. I don't know what the efficiency of that recovery is, but it is FAR less than 100%. It may be better than grinding up brake pads and heating the disks. It for sure calls for more equipment which costs more to make and weighs more in the vehicle and needs to be maintained.

A full scale energy audit should encompass special mining of rare metals, such as the nickel that goes into some auto batteries, the recycling cost and probabilities of plastic and metals revoery from junking the entire automobile (BMW was talking about doing this in the 80s), and the lifetime energy expense.

The U.S. government was issuing guidelines on electrical equipment lifetime cost in the energy sector over fifty years ago.

These are not new concepts but they are also not universally applied concepts. Hence marketing is still way more dominant in decision making than plain boring old engineering economics.

For those interested in attacking the capitalist system, these concepts of engineering economics came out of that system. Going the path of government control, sometimes known as 'socialism' may or may not result in these concepts being applied because human interest is always involved, and having a government imposting rules and regs enables much more shade than it does light.