A friend use to work for Toyota Frontier, once a japanese technical fellow was there from Toyota, He claimed that in ideal circumstances Cuore can exceed 20Km/Liters.
My Friend who was Deputy Service Manager (Maybe) got him in a cuore and drove himself with 4 liters of fuel in a can.
He never exceeded 70 Km/Hr in 5th gear and went for a long run on GT Road.
The car gave 27+
I had my reasons to beleive because some of other staff there also seconded the same fact.