I agree with you from my experience 100 % PJPJ72 wrote:The manufacturers also advised against using synthetic 2 stroke oil and 4stroke engine oil, well, until they brought out their own synthetic oils that is. I have never seen any engine damage caused by use of a higher octane fuel in something with 91 octane recommended, (in 30 years of working on engines), and as for manufacturers, sometimes they don't give us all the information, just what they think we need to know, it's not always to the benefit of the consumer
But, at the end of the day, when an outboard manufacturer specifies using 91 octane,
Its them that warantee the engine, not you or me ! they will try to get out of any failures if they can, so why give them an out,
So my recommendation for new engines, be it out board or car,
Use what the manufacturer recommends !!, either oils or fuel.
A footnote, Not all engines can be lumped into that, I've seen catstrophic engine failure by wrong octane levels used in race engines,
But I understand that's not what we are talking about here......