ACCC media release
ACCC report
My own research in Melbourne from a few months ago:
Petrol price differentials - additional cost for Premium unleaded petrol on top of Regular ULP price)
—————————-RON 95—-RON 98  
BP……………………..8…………..16   
Metro…………………10…………..- 
United Petroleum…..10…………..16.5   
7-Eleven/Mobil……..11…………..16    
Caltex………………..12…………..19    
Woolworths/Caltex…12…………..18  
Coles/Shell………….17…………..23



 
 











yeah, i gave up supermarket petrol discounts a while back.
I've also been logging different RON and consumption in my car. Calculating a price/performance ratio.