I have doubts if you would be able to import a brand new 250. As far as I think Japan does not export 250s, you might have to import one directly. And new bikes come with an EFI so consumption would be better, at least 25km/liter, I believe.
On my Yamaha I have noted a maximum average of between 17`18km/liter (normal rpms), however a maximum of 20km/liter is very much possible. I am happy with the average..