99 octane?

[Alex]

Recently in Denmark Shell offered 99 octane for the same price as 95 (a limited time only kind of deal). My Yamaha dealer told me that the engine would ''run cleaner'' if a higher octane is used. Found some threads online but opinions seem to be divided. What do you guys think?

 

[Nuggets]

Not sure about running cleaner but I do use 97 or 99 in mine as its fun bike and the small cost difference and small tank means I don't reall notice a difference in my pocket. I certainly think I notice a difference in the responsiveness and how hard it pulls, IMO it feels a little more livelier on the higher octane fuels.

 

[gregjet]

Ok. Quick fuel note. Higher octane rating does not necessarily mean more power. The motor will only run :"cleaner":if the compression ratio AND head design requires harder igniting fuel ( actually higher activation energy fuel) . The higher the octane the harder it is to get it to burn. So for very high compression ratios or turbo and supercharged motors you have to have higher octane to stop compression preignition ( knocking). The Yamaha has neither high enough comp ratio nor poor head design so 99 ( 98 RON) is a complete waste of money. There is a story that higher octane fuel is cleaner and fresher ( important) but I can see how the opposite would be true . Higher octane fuel is sold in considerable less quantity and is likely to be sitting around longer. On this point I stand to be corrected by people who actually know. Unless you are using the motor are high throttle openings in most countries std. fuel will be more than adequate ( ok maybe eastern euro countries and 3rd world countries this isn't true). 95 RON equivalent I feel would be worth it if you use wide throttles often ( autobahns?). In Australia with the limited throttle opening MT07's even 95 may be a waste of time and, as importantly , money. If you have an unrestricted MT, I would buy the 95RON ( equivalent) but 91RON would be fine for most people short of track work or very high speed touring.

 

[Nuggets]

I've got an MT-07 so of course the throttles are always cracked open!

Maybe it's fractions of improvement but I'm sure it feels that little more lively on RON 99, who knows maybe its time I go see the doctor!

 

[Alex]

I filled up a coupe of times during this period and I feel occasionally that it pulls a bit better. I can also sense a small difference in sound if that's possible (running on a Akra without db )

 

[tw586]

I have tried both 98 and 95 RON fuel and can not tell the difference however here in australia 98 is a good deal more expensive than 95 so I use 95