[lkchris]

No, it's fuel economy that drives it.

The turbocharging is coming with smaller displacement.

Smaller displacement means better economy, but if you want efficiency and forced air is more dense it requires more fuel, but nothing like greater displacement requires. Engines are seldom run at their peak horsepower point, and when they're toodling around smaller displacement is the path to better fuel economy.

Remember that the push for better fuel economy has nothing to do with cheaper fuel--all these motors will require premium fuel.