Must Be The Fuel

I have been wondering, lately, why is it that both my car refuses to revert back to their much nicer fuel consumption of old?

STELLAR used to do 16-17km per liter at 60kph. The Warrior used to do similar figures too, at as much as 110kph.

They both do 12-13km per liter now. Like what!? Even 2 liter cars can better 20km per liter. My dad's 2004 Camry sees 40km per liter all the time, even at 120kph!

So I accepted the limitations the Warrior have over mileage, but, at least, replicate the old consumption of yours please.

I know that Warrior has been decarbonized, had its throttle body cleaned, had it's oil changed back to thinner viscosities, and so on.

Then it dawns on me, it must be the fuel then.

I have been using RON95 lately, because RON97 is currently the premium priced petrol of choice.

I think, I must revert back to RON97, for both cars, and see how things goes.