Wow those are some seriously impressive numbers. As soon as I do an MPGuino I'd love to do speed vs. MPG with the VX. I'm actually quite surprised to see the peak MPG of the mirage come in so low, personally I would have expected it to be higher, more like the 40 mph range.
I don't know any of technical details of the car, but I can't imagine that at only 40 km/h it's already got the converter locked in a higher gear? Maybe I'm wrong though, it's happened once or twice before
EDIT: Nevermind, I just realized that is a 5 speed car, manual (?). At 1200 rpms I can definitely believe the economy.