There haven't been many breakthroughs in the past twenty years in regards to fuel efficiency. They're just gaming the numbers at this point by making the engine

There haven't been many breakthroughs in the past twenty years in regards to fuel efficiency. They're just gaming the numbers at this point by making the engines have higher and higher compression at the cost of making them less and less reliable. Maybe old cars being dramatically less fuel efficient was true in the 90s when an "old-car" was from the 70s.