FE changed after 3 weeks trip

[GasSavers_smoke]

Hi all,

Just switched to Honda Stream 1.8 5AT for 4 months,
it has a build-in FE gauge, normally I've got AVG 8.8~9.2 Litre per 100km.

But recently, after it parked for 3 weeks, now I can only get 10.0~10.5
in AVG.

It has oil/filter changed, tyre pressure checked, bettery reset,
everythings are fine.

Any suggestion of what to look for ?

Thanks.