Down under we are spoiled for choice.
We have 5 types of fuel -
ULP - standard unleaded petrol RON 89-93 depending on which way the wind blows,
PULP- premium unleaded petrol RON 95-96
UULP- ultra unleaded petrol RON 98-100
E10 - ULP+1o% ethanol RON 91-95
E10P- PULP+10% ethanol RON 96-98
variation is across batch and brand.
Pricing is also a nice spread. E10 1-2 c/l less than ULP; PULP at 6-8c/l above ULP; UULP 8-12c/l above ULP and E10P 1-6c/l above ULP
I have a MY06 subaru forseter. I get consistantly 10-10.5 l/100km on one brand of E10 [95RON]. Trialed over same route per week for 8 months. I switched to PULP of another brand 300m down the road and get, consistantly, 8.2-8.7 l/100km. By buying a better fuel I burn less petrol as a component of the fuel i.e. better than 10% improvement. To cap it off, at $1.50/l I get better km/$ using PULP over E10.
It pays to shop around, and do Km/$ calculations on the petrol portion of your fuel.

Schroedinger's mouse: a cat can't live on probability alone.