No one mentions the fact that your house is a big contributor to greenhouse gases- more so than your vehicles.
Commercial planes? Really big producers! Per passenger much more than any vehicle.

Of course industry is never bothered, although there are many ways in which they could reduce emissions. Because changes would cost them money, nothing will be done unless government forces them.

SUV's and vans on truck chassis (although modified), such as Durango, Suburban, Yukon, etc. are in a different class than Ford Explorer, Jeep Cherokee, etc. Weight, type of transmission and ratios, regulations less strict for light trucks, etc.

Bee-Dubya-ell is partly right about 6 vs. 8 cyl. use in some vehicles. A case in point is the Jeep Cherokee. For off-road use, a skid plate and other protection may be added to the sixes. They won't fit on the 8, which is a highway machine (New models now, may no longer apply).
That said, most 6 and 8 cyl cars achieve the same "green" rating of about 6. There is little real difference.

BMW is testing 10 hydrogen models on the road in California. Saw the item on TV about a year ago, but have heard nothing since. Anybody know more?