There would be riots in the street if we tell people that they have to put 92 octane as a minimum on their v8 Explorers or chevy trucks so they can drive to work in bumper to bumper traffic while talking on their cells and/or putting make up on. We are driven by economics not the environment. NZ has had a "clean air" policy for years and this is part of that. Other countries are probably way ahead of us as well. My guess is cars have to run on cleaner fuel so I assume car manufacturers tune their car engines for that market and for the minimum octane and that is why they ask for 92 there.