Well my circumstances are quite different, wife drive it around 700 km to 900 km a month and i am changing engine oil roughly every 5 months.
V-power is marginally expensive than regular fuel for sometime, plus it give me peace of mind and will be beneficial in the long run(on Engine, Cat, injectors, fuel system etc etc, the manual recommends it but its not go there)
4 cars we have old civic, Wagon R, Cultus and Pica (Big Family we have).
Cultus and Wagon R are Rust buckets with lousy build quailty, Seating wise Wagon R is much better that Cultus, i would perfer Wagon R over Cultus if i have to travel long distance.
if we are just going to discuss fuel economy, yes Suzuki is the best out there for natural aspirated engine in 600 to 1000cc category.
3 to 4 per km low fuel average during summers, I am willing to take.
P.s Cultus gives us 15 with AC and 17 without it and Wagon R is also in the same ball park range.
You can achieve the same in Pica, how strip the whole interior just leave the drive seat, hopefully we will loss 100+kg and voila same 15 km on ac and 19 km average on congested roads.