So Really, What octane to run?

[sledhead ut]

At the end of last season there was a lot of hype about premium/91 vs. regular octane fuel. Some said the sleds ran as good or better on Reg octane fuel. So the question is: For a stock or slightly modded sled, what is the verdict. Do we really need to spend the extra coin for higher octane fuel. I took an interest in this last year, but I guess being the end of the season and people going into the molecular breakdown I didn't follow or retain it.
Thanks for any input.

 

[BeerFart]

I guess it matters more on what you ride. I ride an 06 m7 and tried 91 and it seemed to run worse. My buddy has an identical sled with a shaved head, a y pipe and a fuel regulator and he still runs cheap stuff. On the other hand i think most of the doos require premium.

 

[sledhead ut]

I'm coming off a Doo. A lot of people were saying that now a days the sled are set up to run on reg. fuel, and actually run worse on premium.

 

[Interceptor]

Octane "slows" the fuels burn - thereby avoiding detonation or preignition. On a stock sled you just run what the manufacturer says to run - anything more is a waste of money, no power gains to be had.
"slightly modded" is the grey area - most mods involve increasing compression or increasing timing or increasing heat in the combustion chamber - any of which could require more octane to avoid damage.
If she is a stocker though, dont bother

 

[sledhead ut]

OK, so lets say the sled is only pipe/can and air box. Is that enough justification to go higher octane?

 

[boostjunky]

the old d&d 1010 with twin pipes and k&n filters ran best on reg fuel. tried av gas which I believe close to 100 octain. ran 91 octain. finaly went back to 87. seemed to work the best

 

[Coldfinger]

My observations for stock engines -
In the mtn regions many fuel stations offer 85 octane. I have never owned a vehicle which stated less than 87 in the owners manual. I suspect the reason is at altitude your compression ratio is lower due to less air density therefore you can run lower octane.

My Summit X requires 91 octane but it also includes clutch settings for sea level with no mention of needing to run higher octane at sea level. I believe the 91 requirement begins at sea level. Refer to paragraph 1.

Has anyone ever dyno'd a sled engine at 8,000' or higher to see the results of various octanes?

 

[milehighassassin]

IF you have a high comp head, premium.

IF you run at higher elevation you can probably run regular.

 

[RMK SeVeN]

For M-Series sled the book says run 87 only...

 

[oregunrmk]

Ive tried both and compared in identical 600ho's. Your wasting money if running more than reg in a stocker.

 

[SafetyBob]

Octane depends on compression, if everyone posts on what compression and octane they are running you will end up with a chart for future use.
Thanks Diann

 

[snowdad4]

also, elevation comes into calculation. the higher the elevation, the less octane needed. just make sure your covered if the snowpark's elevation is considerably lower altitude than where the true days ride is. (no long wot pulls out of the parking lot).

 

[94fordguy]

So to get this all straight, for 5-8K feet, it would actually be beneficial to run regular 87

What about the premium setting on the key?

 

[little_orange_cat]

i run 119 it seems to work the best for me but this year i think i might step it up and try out vp's import fuel

 

[stonecold]

ethanol

here in oregon we have changed over to 10% ethanol but some of the stations are selling premium without it and I think that would be the way to go as I understand the ethanol attracts water.

 

[PJ-Hunter]

The owners manual on my xp states that I have to use 91.

 

[Coldfinger]

The owners manual on my xp states that I have to use 91.

Does the owner's manual say you need to run an octane rated higher than 91 at sea level?

 

[Bubba700]

So to get this all straight, for 5-8K feet, it would actually be beneficial to run regular 87

What about the premium setting on the key?

If your talkin about on your 02, It was explained to me that the Prem. setting changes the timing and has nothing to do with what gas you are actually running. Could be wrong but that is what I was told.

 

[Flit-e]

If your talkin about on your 02, It was explained to me that the Prem. setting changes the timing and has nothing to do with what gas you are actually running. Could be wrong but that is what I was told.

you are right the "premium" setting is just a timing curve change

 

[rotax]

The owners manual on my xp states that I have to use 91.

whats intersting about this is, i believe its for sea level? to cover their a$ses.

wonder if they need that at 8k+ . . where compression goes down drastically.

Octane depends on compression, if everyone posts on what compression and octane they are running you will end up with a chart for future use.
Thanks Diann

By what i've understood, theres more to it than just (cranking) compression? No?

Timing.
Port sizes.
Pipe sizes/restrictions.
Squish.
Piston.

Basically all "engine" related mods will determine required octane. And also what can bring confusing. Unless one shop does all your mods/mod work and knows what works with each other and so on. Or simply...play the game of 'try n learn'.