To 91 or Not to 91 Fuel Octane

joel97mustang · Nov 4, 2011

I just purchased a pair of new stock 2011 M8's with the HO engine and now I have to run 91 octane according to spec. I am wondering if anybody has run 89 with octane booster or some other cheaper variation of fuel mixture with any success??

It seems that you get nailed for 91 at the pump because you would be fueling a Porche, Audi or some other high priced ride.

I will run 91 if I have to.

It is impossible to snowmobile and be a tight _ss or cheapskate but I keep trying:face-icon-small-ton

Thanks

mr.deeds · Nov 4, 2011

If you use octane boost to get up to the 91 rating... you will be paying alot more than if you just bought premium in the first place. That stuff doesn't do much.... and if it says it boosts your octain 10 points it really only moves it from 89 to 90, because each octain has 10 points.

luv2sledmt · Nov 4, 2011

Here my thought. 91 is 10 cents a gallon more than 89, so to fill your 11.5 gallon tank you will be spending just over a dollar more with 91 rather than 89. So when you include the 50 to 75 cents a tank worth of octane boost, you will be saving approximately 50 cents a tank and be gambling with it working. 91 octane seems like a easy decision for me.

06m7 · Nov 4, 2011

i always run 91 and my buddy same sled only runs 87 never seen a difference at all in performance and mine had octn light come on twice and his not at all so do what u want i still run 91 just not sure if i should be or if its worth it

backcountryislife · Nov 4, 2011

we run 85 or 87 in the 91 machines up here, but down low the 11 is a pretty sensitive motor, octn comes on pretty easy on most of them.

Dam Dave · Nov 4, 2011

depends on altitude I run what ever but sled is never below 7000'

Twostroke · Nov 4, 2011

dude it's like $1.00 more per fill up, $1.00!

backcountryislife · Nov 4, 2011

Twostroke said:
dude it's like $1.00 more per fill up, $1.00!

and running higher octane cost you performance as well.

There's a sensor for a reason, use it to find out what you need to run, then run it.

If you're running a 1000... a could understand the hesitance to chance it... but on the 8, it's kinda silly.

mynewuseddoo · Nov 5, 2011

Just put an 09 head on it and run 87. I've got one for sale if you want.

Coldfinger · Nov 5, 2011

backcountryislife said:
we run 85 or 87 in the 91 machines up here, but down low the 11 is a pretty sensitive motor, octn comes on pretty easy on most of them.

Agree, depends what altitude you are running. If you run at sea level, do you have to run higher than 91? The 91 rating is likely at sea level.

The more altitude the less octane needed because the air gets thinner and thus the engines compression goes down.

This is why many mountain fuel stations sell 85 octane.

Spiced Wafer · Nov 5, 2011

this is the wrong sport to be penny wise and a dollar short on things...don't short your self over a couple of bucks in gas

WyoBoy1000 · Nov 5, 2011

any thing under 4000ft I wouldn't, or if it has ethanol I wouldn't run under 6000ft. at 10000ft up I would try 87 non E

backcountryislife · Nov 5, 2011

WyoBoy1000 said:
any thing under 4000ft I wouldn't, or if it has ethanol I wouldn't run under 6000ft. at 10000ft up I would try 87 non E

at 10k we're running 85 with ethanol. Non E doesn't even exist around here anymore. IMO, the whole ethanol thing is WAY overblown.
If, after we've got some miles on it, we start getting the ethanol message, Ill switch, pretty simple.

Worrying about what octane on the 800 seems like one of the most pointless conversations there are imo.

x-5 · Nov 5, 2011

mynewuseddoo said:
Just put an 09 head on it and run 87. I've got one for sale if you want.

Yes Or trade me your head for my 09 head :face-icon-small-hap

Jordo · Nov 5, 2011

Ok u guys r so cheap. It's 8 cents more a gallon. And if u run a 10+ u will get an Oct code and it will put u into limp mode

mynewuseddoo · Nov 5, 2011

x-5 said:
Yes Or trade me your head for my 09 head :face-icon-small-hap

Deal!

knightracer_08 · Nov 5, 2011

seeing as this is a fuel issue and some are willing to spend the extra cash to keep a motor, I have discovered Chevron is carrying 94-octane 0-ethanol these days. Im going to be running it as well as some 100:1 pre mix, tired of rebuilds.

AKLankford · Nov 5, 2011

quick question on the octane ratings.

So here in Alaska i have never seen 91 octane. Highest we have is 90. Is that 1 octane a problem since we all ride at 0-3000?

backcountryislife · Nov 6, 2011

knightracer_08 said:
seeing as this is a fuel issue and some are willing to spend the extra cash to keep a motor, I have discovered Chevron is carrying 94-octane 0-ethanol these days. Im going to be running it as well as some 100:1 pre mix, tired of rebuilds.

Rebuilds?

Because of lack of oil?:face-icon-small-con

Because of lack of octane?:face-icon-small-con

WHERE, WHEN? Show me ONE person who has actually had an M8 go down due to det.

As to oil... the issue is a linkage that can fail, and that 100:1 will let your sled blow just like no oil at all will.

Sorry, but I'm just blown away at the fear-mongering that some of you guys buy into.:face-icon-small-dis

As to limp mode, I'm not suggesting that someone run too low an octane every day, simply that it's not hard to figure out since the det sensor protects you from damage. One day to see what you really need.

It's NOT the $$. You will run the strongest with the least octane you can safely run, running more just costs you HP. (the dollar a tank is a non issue, we're not talking about running 116 here!)

Lankford, I've seen a number of people on ACchat who have mentioned never having any problems with the 90 in AK, some were pretty worried about it, but they found it worked fine.

WyoBoy1000 · Nov 6, 2011

backcountryislife said:
at 10k we're running 85 with ethanol. Non E doesn't even exist around here anymore. IMO, the whole ethanol thing is WAY overblown.
If, after we've got some miles on it, we start getting the ethanol message, Ill switch, pretty simple.

Worrying about what octane on the 800 seems like one of the most pointless conversations there are imo.

I agree, I was stating it more as a starting point and if nothing happens then go lower, I still don't like E, all my engine failures happened with it (91e). But it could have just been chitty gas.

For the guys saying where being cheap, we don't care about cost, we care about power and to much octane you will loose power. The sled should put out around 160hp at 0ft, at 10000ft you cut that by 33.333% and it drops you down around 115hp so your not going to need that much octane unless you mod it and get the power back up. HeII we are running 6-8lbs of boost on 91 octane around 10000ft without deto, do you really think you need it on a stocker. Like mentioned the det sensor will let you know.

To 91 or Not to 91 Fuel Octane

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