This is what puzzles me about the diesel engine tuning in the iQ. Instead of optimizing the drivetrain for fuel economy (like for the 1.0 petrol), the diesel seems to aim for performance with non-eco tires, high power output and large displacement (1.4 liter!)

I don't know of any smaller diesels in Toyota's engine palette, but a 0.8l or smaller eco-diesel with stop-n-start technology should at least be considered now that the competition seems to go this way.

The particle filters from Toyota are extremely effective, but what does it help when the fuel economy isn't class leading?