Part of the article..anecdotal info from a Castrol tech
Yesterdays fuel price for 91RON was $1.27/litre close to me. That usually equates to $1.47 for 98.3: 91 (standard non ethanol) is basically just straight unleaded fuel as refined no additives other than base anti oxidants. He said that most of the later unleaded type bikes (so post 1985) would run quite OK on this fuel but he agreed that because of the nature of the fuel there would be build up of soft gummy deposits over time.
4: 95 (premium non ethanol) higher octane base fuel more suitable for the older higher compression engines but his opinion was that any of the bikes would benefit from using this fuel. Contrary to what I thought from my 2,000 induction to unleaded fuel, he thought that the higher octane would help some models and bikes but that the main difference was the "Vortex" additive pack in the fuel which was primarily a continuous cleaner. He pointed out that these additives were produced by Chevron / Texaco and had had such an amazing result since their introduction to Australian fuels "a little while ago" that they were now using the same additive in their diesel fuels. the upshot of all this was that in his view, with the types of main stream carburettors used on our bikes (so BING CV's) this was the best alternative.
5: 98 (super premium non ethanol) the highest octane ULP available in Australia. It has the same additive pack as 95 with a few extra tweaks (which in his opinion would make very little if any improvement on the fairly basic fuel system which exists on our bikes. When I explained to him that I had a 1974 model 750cc model that pings on anything but 98 regardless of any fix short of de-compression plates that I have ever tried. He said that of course, in an event like that the higher octane fuel COULD overcome that issue but that the only way to know was to run a few tanks through. He did say that he thought 98 was an expensive option if the bikes were running well on 95 or even 91 but he did day several times that he thought 95 was the correct fuel to use.
I've exclusively used 98, but over the weekend I tried 95 because it's cheaper. I managed to ride 285 kms at hwy speed, no more than 125kph, but mostly around 110kph. I didn't hit reserve which is at around 21 litres in a 24 litre tank, however milking some petrol for the mower yesterday showed I was very close to reserve. The previous tankful had me fanging a little for 272 kms thru the mountains and I got 15.6kmh/litre over 272kms.
Hardly any difference to the economy from the 98 and the bike ran as well.