I've been tracking the km and L on fill-up, and it's been pretty accurate. I've been shocked at how far I can go between filling up. Once I put the 2" lift kit and snow tires on I expect significantly worse mileage for the winter.From my experience with a Prius and now this Sienna, Toyota's MPG calculator tends to be about 5%± too optimistic, so you may find out that in reality you clocked 40 mpg or 5.9L/100 km. Nonetheless, this is incredibly high fuel efficiency for a vehicle of this size.
I shall not comment about the Smart car