my mum own one ... FC is about 8.5km/l ... not that good i think ... i drove few time from terengganu to penang or to KL need to refill the tank to reach there..
I made one myself at home ,
i think it works not bad ,
material = plastic bottle , gas hose < i'am using 9mm transparent type > and sponge like thing that you often get when buying delicate items like computer...