My GT-R did 10L/100km once. But usually it does 14L (when I daily drove it).
My Liberty does 11L average, stop-start kills it (which is why hybrid cars makes so much sense in cities/suburbs).
Always fill 7 Eleven (Mobil) 98.
It makes sense to try difference sources of fuel. Also fuel can vary between stations, so brand doesn't usually matter. Except if it's Caltex or United, not putting that crap in my cars (I don't need ethanol fuel).