There are a lot more variables than just engine capacity when
comparing FC. Mods, tyre size, driving style, turbo or NA,
4WD/RWD/FWD, different manufacturers, synthetic or mineral oil, car
weight, etc.
As an indicator, efficient Jap cars will give you max:
14km/l for 1.5liter engine (e.g. Vios)
12km/l for 1.6liter (e.g. Corolla)
10km/l for 2liter (Camry)
Some Honda cars give even better FC (e.g. Jazz) and Hyundai cars
usually give poor FC. Sunny has poor FC but Latio is similar to the
above.
All the above based on talking with frens and personal
experience.
By the way, Yamaha Spark gives 50+ km/l 