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Message started by 2011suzukis40 on 04/22/12 at 05:14:15

Title: octane
Post by 2011suzukis40 on 04/22/12 at 05:14:15

Which octane is best for my 2011 suzuki s40? The dealership says you can use 87 but "it likes 91". The manuel says atleast 87. I have ran 1 tank of 87 octane and it ran good. I put 89 octane in it and seemed to run better. I last filled up with 91 but havent ridden since. Does anyone know what is best for the bike?

thanks

Title: Re: octane
Post by LANCER on 04/22/12 at 05:27:23

Compression ratio is the primary indicator for what octane fuel to use.
The LS650 engine in stock form has a ratio of 8.5:1 and 87 octane is the appropriate fuel. If your engine is running lean, and therefore hotter, that may affect the need for going to 89 octane, but I am not sure if that is a fact.
You should ask Oldfeller about this, he is much more knowledgeable than I am in this type of tech detail.

Title: Re: octane
Post by Serowbot on 04/22/12 at 06:21:13

Regular unleaded...
Any performance gain from higher octane in this bike will be imagined, it just doesn't have the compression to require anti-knock additive.
... and fuel without added anti-knock additive, naturally has more burnable fuel in it... (only a small difference, but.. more)...
Higher compression engines don't use high-octane gas because it makes more power,... they use it because the regular gas would pre-detonate at the compression level they are using...

Title: Re: octane
Post by 2011suzukis40 on 04/22/12 at 12:52:28

1012131351575857494B511612220 wrote:

Will higher octane hurt my engine???

Title: Re: octane
Post by Cavi Mike on 04/22/12 at 13:04:20

The higher the octane, the less tendency it has to detonate. Detonation is when a fuel will auto-ignite - that means it will ignite from heat and compression alone, without spark. This only happens on higher-compression engines. If your engine doesn't have a high enough compression ratio, higher octane gas will not make your bike run better. In fact, it's possible your bike will have less power because engines typically run with a small bit of detonation which creates multiple flame fronts - this means the fuel ignited in multiple spots, not just from the spark.

In short, no, you can not damage an engine with high octane gas. High octane gas doesn't burn hotter, it doesn't contain more energy, it doesn't burn cleaner; it just resists detonation. That's it.

Title: Re: octane
Post by Serowbot on 04/22/12 at 13:17:19

Ditto what Cavi said,.. and a tankful won't hurt...
... but, for the reasons Cavi stated... constant use could build up some carbon in the head over time...

Title: Re: octane
Post by Dave on 04/22/12 at 15:47:23

Thank goodness I finally found a website were people understand what higher Octane fuel is for. I hate hearing false rumors about higher octane fuel burnng hotter, making more power, etc.....when I know it doesn't.

Running regular is fine.......run some 89 if you want when the summer temperature goes over 90......but you may not have to. The thing to listen for is "detonation"- if you hear it when you roll on the throttle under a load it means the mixture is wrong or the fuel is too low of octane.

Title: Re: octane
Post by Realbtl on 04/22/12 at 16:28:16

This raises an interesting question for me. Here in Montana I can often get non-ethanol gas though it's almost always premium. I usually go for the "real" gas. Is there any consensus out there on this? Thanks

Title: Re: octane
Post by Oldfeller on 04/22/12 at 17:04:15

I still run regular gas. In NC regular means 10% ethanol by law, and ethanol effectively raises the overall knock rating of the fuel (it is listed in the anti-knock additives on our listings) even as it reduces the regular fuel's energy potential (alcohol is a thinner, weaker, cooler burning fuel compared to gasoline).

Unless you put in a hot high compression piston you really don't need to run premium gas in a Savage.

Premium gas around here has sat around in various tanks for a VERY LONG time -- nobody ever buys it, so it isn't fresh gas by anybody's guesstimation.

Title: Re: octane
Post by SALB on 04/23/12 at 13:22:12

I bump the Octane up 2 points in everything I own, in the heat of summer. 100 plus degrees and less than 15% humidity is on the edge of being extreme. [smiley=evil.gif] Last winter I accidently ended up filling up with 85, and didn't have a problem, although I wouldn't make a habit of it.

Title: Re: octane
Post by Savage_Rob on 04/23/12 at 14:15:21

Yeah, higher octane is to inhibit predetonation in cases of either high compression or high heat. The compression in our bikes is not sufficient to warrant it. I have considered using higher octane in the heat of summer but I'm not sure whether riding my air-cooled single in 100+ degree TX heat is sufficient to require the higher octane or not. I have not noticed any knocking or pinging though.

When it comes to non-ethanol fuel, if I had it available, I believe I'd use it... at least in my bike and any small engines like lawnmowers, chainsaws, etc.

Title: Re: octane
Post by WD on 04/23/12 at 15:41:25

Mine always ran best on the cheapest garbage gas I could find. Has always been fed a steady diet of 10% ethanol blend and other than needing to change the fuel line every other year had no problems. Which you should really do anyway on an aircooled bike, the line does get crispy over time. Especially the ultra flimsy stock gas line.

When it gets hot, my bike gets a really diluted 2 stroke mix. 1/2 ounce of cheap ATF every 2nd or 3rd tank. Doesn't seem to have as much decel popping. And less fuel tank rust. Have been using it since new (2/98). Does it hurt it? No. Does it need it? No. Does it help it? No clue, but I haven't had some of the common cheap gas issues (petcock failures, slide scuffing, etc).

Title: Re: octane
Post by justin_o_guy2 on 04/23/12 at 17:26:51

Nothin wrong with a little slickum in the pushmoline,,

Title: Re: octane
Post by thumperclone on 04/23/12 at 23:23:36

im at 4500 elev
once the jetting was rite have had no props
the GRAND MESA is our valleys(4500) eastern wall..
have had no props goin up and over it every year since o6

Title: Re: octane
Post by Savage_Rob on 04/24/12 at 10:03:41

7E6D290 wrote:

Yeah, I used to run a little MMO in previous bikes every now and then. Haven't done it in this one yet but probably will start, now that it's been brought back to memory.

Title: Re: octane
Post by bill67 on 04/24/12 at 10:42:20

You will have less power with higher octane gas,It burns slower so its like retarding the spark.