I'm sure, but don't you think they had much less of a grasp on things back then? To meet emissions in the 70's, they dropped compression through the floor, which killed efficiency. Totally the wrong move. All of the steps they took made efficiency worse. I think there is much more understanding now about the combustion process now. For example, look at some of the newer Mazda Skyactiv engines operating at super high compression ratios. Hey, you could be right, no doubt. But, I believe that we've got a much better understanding of the basics and are now just milking the remaining gains, which have diminishing returns. It will be interesting to see where they find the gains. The real stop to development will probably be when battery technology comes of age and everything goes electric.