Australia generally has a choice between 91, 92, 95 or 98 octane unleaded fuels. The ideal fuel for your motorcycle depends not only on engine design but also whether your bike owns a re-mappable ECU/can have its ignition advanced/retarded. As a standard, most bike shops will recommend using 95 as pretty much a safe all-round petrol.
Every bike should have an Owners Manual, this is where the people who know your motorcycle the best, know what is best for it; the Manufacturer and this is always the recommended fuel. However, if you do not have the resources currently to source the information out or you have made some modifications and the engine doesn’t seem to run too well anymore, the key to finding out which fuel is best for your bike is trial and error.
If after you change the fuel and suddenly your engine is ‘pinging’ or ‘pre-detonation’ is occurring, it’s most likely that it is not the right fuel for your bike, try going to a higher octane (slower burning fuel) or a lower octane (faster burning fuel). Unfortunately, some petrol stations can, at times, sell a very poor quality of fuel that contains water/rust or just stale petrol. This can cause many problems down the track. It also may require a flush out of your fuel system, whether it be fuel injected or carburetted, which can be costly. In the end the best and easiest way to know what fuel your bike will run on is to have your bike dyno tuned by a trained professional.
Ethanol fuels have become more common, but my personal opinion is they are not very good for bikes. They raise a number of concerns for me, the first one is that you are not getting 100% fuel. You are getting 90% fuel and 10% “filler” or alcohol. Ethanol fuels also hold water in suspension within the fuel, that is, the water and fuel do not separate out. Water is heavier than fuel (a litre of fuel weighs 760gr, a litre of water is 1 kg.) This is why when you get water in your fuel the bike stops. It runs to the bottom of the tank and gets picked up by the fuel tap. Ethanol stops water from doing this, and thus mixes the water into the fuel. For a bike (or car) that sits unused for any length of time, this means corrosion can start inside the fuel system, including pumps, lines, and injectors. Ethanol fuel can also react with some tank coatings, and distort acrylic or plastic tanks.
