Fact - The base fuel that the majority of fuel companies in WA use is from the BP refinery. I say most because some cheaper brands like Gull, Peak, United et al, import some of their base from Singapore as they may get it cheaper. Hence, why you never know what type of fuel is in them
Fact - All the majors spend millions of dollars on chemist, physicists to come up with mixtures that give them an edge over their competitors, so even thought the base is the same the end product is totally different.
Fact - BP Ultimate 98 is the only 98 RON fuel that is made as a 98 fuel from the start in WA. Shell do not supply their Optimax anymore anywhere in the world, they supply V-Power over east because they have refineries in Geelong (Vic) and Clyde (NSW) and ship/truck it to QLD, SA. Transport costs prohibit the supply in WA and they do not want to give BP their ingredients for them to make it at Kwinana, competitive forces at work. All the other 98 fuels in WA are made from additives, so to speak.
Fact - Not all fuels are the same, and anyone who thinks so is kidding themselves. A perfect example of this is Ethanol fuel, even with the same Octane rating you get less energy from it then an equivalent RON non ethanol fuel. Sometime you can get more power from 95 RON than 98 RON fuel if the density of the 95 RON is greater, but only if your car doesn't need the heat protection of higher RON, e.g. turbo cars.
Fact - They all have to comply with governemnt regulated maximums in sulphur, benzyne and minimums in RON but there are a lot m ore other factors that are not regulated and the different fuel companies use this for the competitive edge.
How do I know all this, I work for one of our fuel majors and have lived both here and in Vic. I can honestly say that the best fuel in WA is BP Ultimate 98, but overall the best is Shell V-Power, as I used it when I was in Vic.
So, go on and use the cheapest fuel or the most conveniant location on your pride and joy and you certainly will not be getting the most out of it and possibly damaging it.