Which octane

[johnster]

I'll give 89 a shot and see if it makes any difference. I might just be hearing normal noise under hard acceleration.

I don't know if you're running an open airbox or not, but if so, the intake sound of air being sucked into the velocity stacks could very well be mistaken for knocking to an untrained ear.....Under hard acceleration, my open airbox is loud as hell.... :e:v

[ducatiz]

unfortunately, most people wouldn't know they are having problems with their engine due to octane unless the crankshaft blew up on them.

mileage is a function of a lot of things and unless you can duplicate the EXACT same conditions (speed, temp, load, compression ratio, etc) comparisons between tankfuls of X octane are nearly useless.

not to mention that gas from different suppliers can have a variety of differences in your engine.  Chris at cycleworks has pointed this out -- you need to test X octane from several suppliers to get an idea which formulation is best -- which matters more if you have a hicomp engine though -- the stock desmodue is very forgiving.

i used to ride up to albany and regardless of the type of gas I used, I would always get about 45mpg.  fill it up with 87, or fill it up with 93.  and that is riding at about 80 the whole way up I87 from NYC.

however, the tailpipes were noticeably more sooty from the 93, but acceleration and cruising was the same (or very close)

and the temp gage noted that the engine was running hotter with the 87 -- about 10 degrees, and this was on days with the same temp (or within 2-3 degrees) in the late spring (so low 70s)

there is a reason the factory specifies 95 RON (euro), because they designed the engine.  They don't make any money off your gas usage and the engine isn't going to blow from putting in higher octane than necessary.

it really is best to follow the manual for the most part. 

I use 89, or I mix 87 and 93 50:50 when i am feeling anal (gives you 90 RM2 and it is about a nickel/gallon cheaper to do)  Engine seems to run a bit cooler than 87 and pipes are not as sooty.

To check soot, use a shop towel and really wipe out the tail pipes so you can see metal.  you can't measure the actual soot, so you measure the buildup after a number of days. it is very ad-hoc so you need to make sure your driving is the same for those days.

manual says use full synth 4T oil, are you going to use cheapo store brand dino oil too?

[hypurone]

This also depends on the compression ratio the engine is running. As well as induction method (NA, Turbo, supercharger). For the OP's bike, 87 may work fine, but not so well in my S4RS. Bike lacks power, runs hotter and knocks when it is warmer out (even with a 13:1 a/f ratio). I can get away with 89 but when you are smackin it hard with a higher compression engine I would rather have the "margin of safety" against knocking that 91 gives me.


What??!! I can't hear you over my really loud airbox!!  ;:|

[uclabiker06]

Use 87 or 89, but not 91.  If your anal/synthetic oil guy use 89.  If your car oil in motorcycle guy use 87....Or you could use both "depending on your mood".  wt:

[silentbob]

there is a reason the factory specifies 95 RON (euro), because they designed the engine.  They don't make any money off your gas usage and the engine isn't going to blow from putting in higher octane than necessary.

it really is best to follow the manual for the most part. 

Well the manual states the same octane for the 9:1 compression desmodue and the 12.5:1 compression evo motor.  So, I don't think they put much thought into it other than figuring if they err'd on the side of caution, they would be less likely to be replacing engines under warranty.


I ran 87 octane exclusively in my S4R and after tearing the engine down (40K miles) for high compression pistons, there were no signs of detonation.

[ducatiz]

Well the manual states the same octane for the 9:1 compression desmodue and the 12.5:1 compression evo motor.  So, I don't think they put much thought into it other than figuring if they err'd on the side of caution, they would be less likely to be replacing engines under warranty.


I ran 87 octane exclusively in my S4R and after tearing the engine down (40K miles) for high compression pistons, there were no signs of detonation.

also depends on how you ride.  people who are harder on the throttle will benefit more from the higher octane and people who are softer on it, perhaps like you, can get away with it.

same thing with old VW engines.  we used to make them right at about 7:1 compression by flycutting and shimming the heads.  anything more than about 7.5:1 and we needed higher octane, unless it was just a daily driver that wasn't run too hard.

my whole point was that there are a lot of variables which affect combustion beyond compression and temp and barometric pressure and humidity and blowby etc etc etc etc.

if you put a water mister on you intake, you could even get the octane further down if you like.  i have that on my volvo s70R.  difference is about 8 hp overall.

[Rob Hilding]

also depends on how you ride.  people who are harder on the throttle will benefit more from the higher octane and people who are softer on it, perhaps like you, can get away with it.

snip

Just from my limited exposure, Silent Bob isn't a "soft on the throttle" kinda guy

[ducatiz]

Just from my limited exposure, Silent Bob isn't a "soft on the throttle" kinda guy

it's all relative, that was my point.

[Rob Hilding]

Point taken - just f'n around with you

Way to many variables involved for there to be a definetive answer

[5lv]

You can't just go by the static or mechanical compression ratio. The actual dynamic compression ratio can be vastly different due to cam timing. When you see a mildly tuned engine with a low compression ratio, it's because that with a milder cam(earlier intake closing) the actual dynamic compression ratio is higher than it would be with a high rpm cam with late intake closing.

[ducpainter]

Bruce told me to use 87...unless I wanted to waste money.

[herm]

this thread should be locked

[Howie]

Bruce told me to use 87...unless I wanted to waste money.

Or weasel piss is available   My bike loves 87

[JasonV]

Glad I found this as I've been putting in 93 in my new 696.  Guess I'll try using 89 and see how that goes.  Would love to go down to using 87 to save money if no problems.  

[Langanobob]

there is a reason the factory specifies 95 RON (euro), because they designed the engine.

Mostly what you said make sense.  But I personally am kind of a doubting Thomas when it comes to things that Ducati says.   They may  have designed the engine but they got their initial spec for the belt tightening frequency wrong with the result of numerous too-tight belts and failures.  Don't know if they still do, but Ducati used to also say "Use only Shell Ultra" oil which isn't even available in many of their market areas, including the US.  Also, there is more or less a consensus that Ducati's engine break-in procedure is not technically very good.   

So, all I really know is that I use 87 and my bike runs fine.