Naza Ria / Kia Carnival is definitely one of the MOST gas-guzzling MPVs in the market, and with expensive maintenance too. Worst choice for an MPV.

I'm very sure Honda Stream can achieve very good FC, but then it's really small. Same goes for Wish, but these two MPVs are really overpriced for their size.

Unser FC provided by zacevox sound reasonable, but it's a very aged car. Perhaps good if you're on a tight budget. From what I've heard, Innova's FC is worse than Unser.

My dad said his 2nd-gen Honda Odyssey 2.3L can get about 10-11 km/L on highway drives (driving alone though). Keeping in mind it's in the same size category as Naza Ria/Toyota Estima, I think that's not bad.