I was always under the impression that the higher the octane rating the more knock resistant a fuel would be and that engines with a compression ratio of 12.5 to 1 should run on octanes higher than 100 or its timing should be ........ to prevent knock? ........ timing = less power and that in such a case where fuels have an equal energy content the higher octane would make more power due to less or no retardation of timing?
In general terms and in theory you're quite right there.
The fact still remains that the Superquadro engine(like other current designs) is designed and tuned around the use of 95 RON fuel.
There's no increase in potential for more power or performance for the vast majority of us in going with higher octane fuel.
Unless we have clear evidence of a ........ timing event due to engine knock because we are running 95 RON as opposed to 98 RON. It's all theoretical.
Assuming we are talking about an engine in standard trim.
It may be possible to replicate that scenario on a dyno.
But there's no certainty that it will ever happen in the real world.
It's different in practice.
I have also seen data where a particular engine has made less power on a dyno with the higher octane fuel.
The reason is that the higher octane fuel(by nature), is simply less volatile so it's power potential is reduced right from the start.
In summary.
There has to be a "clearly defined necessity/requirement" to run the higher octane fuel, in order to actually access the full power potential out of any engine.
To get back on topic, and in terms of the issue framed by the original question.
In my experience with both my DUCATI's, they run much better on the 95 RON fuel as opposed to the 98 RON fuel(regardless off the additional additives).
I used to run the 98 RON fuel because I always wanted to give my toys the best I could.
After lengthy discussions with piers in the industry.
A general consensus was reached that the 95 is always going to be the best option for a stocker regardless of state of tune. I made the switch accordingly.
After the change from 98 octane fuel to the 95 octane fuel, I observed a clear improvement in every aspect of real world engine operation with my bikes.
In order to confirm the seat of the pants results, I volunteered the use of my bike for the confirmation dyno run test immediately after a thorough service.
I have since done the back to back dyno run on the same day with the two different fuels.
The first run was with a couple of litres of the 98 in the tank. It was then sucked out of the tank and it was filled with the 95.
The following run revealed there was no performance advantage evident in the 98 RON fuel with using my favourite brand of fuel.
Both fuel samples were sourced from the same location on a main road that has a high turn over, in order to provide the freshest examples of fuel possible for a fair comparison test.
I should add that I also avoid Ethanol at all costs.
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