[Machzzzz1]

What fuel is most likely to hole your pistons.  87oct or 91.  

I was sure the answer was 87.  87 has a lower flash point and i think burns more vilontly then 91.  I think 87 give you more power but makes your machine more likely to detonate.  

91 has a higher flash point and burns slower causing a loss in power but a bigger safty margen.

IS THIS RIGHT.  

Because some guy told me opposite.  

I have never run 87 in any of my machines and have not had a problem.  However i have seen machines with 87 go up in smoke.  

Please let me hear your opinions.

 

[MightyMach]

You are correct.  You only need higher octane if you have higher compression.

 

[SledHed670]

As you increase octane you can also jet leaner to try and compensate.  But then if you fill her up with 87 its burndown city.  i try to run prem when its real cold out as kind of a safety margin.

 

[670HO1]

87 oct. can cause a burn down. A guy I know burn holes in the tops of his pistons on a 97 700 rmk. His sled called for 89 he said I think so that's what he runs now. My 99 HO calls for 91 because of the higher compression but I have ran just 87 a couple of times but I didn't go wot.

 

[MightyMach]

My mach calls for 91 also, but my dealer told me to run lower octane when it was really cold because premium is harder to ignite and runs cooler to begin with.

 

[ballsout1]

Mighty Mach, I hate to say it, but thats just plain heinous....if I spelled that word wrong forgive me, I`m not used to adressing issues ...well..quite that heinous....

 

[speed is everything]

this should sum it up. the higher the octane the cooler it will run no matter what your running it in. i have spent alot of $ having race fuel tested at a lab so i wouldnt burn up a motor worth much much more.the higher octane not only burns faster creating less heat but it will also burn more efficient.happy sleddin.

 

[alta]

In a perfect world higher octane does burn more efficiently, cooler, and yields a higher safty margin.  What no one is addressing is the age of the fuel when you're filling up.  91 octane is generally not purchased by consumers as much as 87 octane is.  Thus, at the stations premium sits in the ground longer than 87 octane  losing octane, and collecting moisture.  I'll take fresh 87 octane over stale premium any day.

 

[kid rocker]

Octane requirements are based "mostly" on compression, the higher the compression the higher the octane.  The higher the octane the cooler the burn.  The lower the octane the higher the burn.  Run what the manufacturer suggests and you should be o.k.

 

[SNORAT]

Also if you are jetted for warm weather on 87 oct and you ride into the night and the temp drops 15 to 20 deg put in the premium as this will keep our pistons from getting hot and melting to the inside of your cylinders as we all no that the colder the air the leaner your sled will run because when the air getts cold the oxy molecules get denser(packed together) and your motor will pull in more oxy for every gulp of fuel.

 

[corvette77]

first off i burn 93 octane in all my sleds damb that stuff must be realy old lol second premium gas has additives to prevent moisture and gas line freeze third it will not lose any octane from sitting in a closed and sealed underground storage tank unless it sits there for many years because it also has stablizer mixed in it already i stored my sled last season with half a tank in it and it ran fine when i rode it the first time this year and i didnt add new gas best way to check for ond gas is smell it if it smells like gas its good if it smell like turpintine dump it

 

[SNORAT]

One thing if the gas does not say ethinal it doesn't have any a gas line antifreeze additives and no it doesn't have any presevitives in it for storage and third yes it will lose it oct rating from sitting in storage. These are a few things I have learned from being a auto mech all my life and the fact I have a freind that owns an Amoco sation and he doesn't fill his premium tanks for this reason he only runs them half ful so he always has to add to them and this keeps them fresh at all times.Anouther thing there is a dif between summer gas and winter gas these are mixed dif at the suppliers.

 

[corvette77]

i guess you will have to anwser this to me i have a77 vette i dont drive but once or twice ayear it has to burn premuim gas because it has 11 to 1 compression i know because i built it from the ground up as you see im a mechanic to have been for 30 years and i have never heard any spark knock and i know the gas is at least 1year old also my vmax4 with hauck 880 big bore sat all summer with the same gas from last year not any probs with it eather guess my gas is diffrent from what everbody else's and it is not methonal

 

[SNORAT]

what you got in the vette what is the timing set at full curve with the fresh fuel you will beable to run more timing cuve before detination. On the sled how far and how hard do you drive it before you head to the station also were do you store your toys because yes as you implied gas will lose it oct rating at a slower rate if stored at a constant temp. But it doesnot have a stabilizer added to it or fueline antifreeze added to it. Also there is a dif between summer fuel and winter fuel as winter blend has to have a lower flash point or your cars won't start right being a mech you should know this as it is common knoledge.But were do you live because that also makes a dif as far as fuel blends I know in northern ND were temps can get to 30 bellow it makes a dif in fuel blends also if your sled goes on it's first ride at 30 above you will not have as many problems with fuel quality as you would if it were 10 bellow.I know were I live if you run 92 non eth your lines will freeze but the 89 with eth they will not so if the pump say 10 % eth added to increase oct this is the one that will reduce line freeze if it don't you will freeze lines or carbs that is why I run iso in every tank ful on the sled because a frozen carb at speed is a melted piston.

 

[Machzzzz1]

What makes octain levels change. What makes 87 turn into 91 at the refinery.

 

[xsivhp]

I tought the equation went something like:

two stroke + ethanol + cold weather = DISASTER !!!  

 

[paul]

First off, in California you can't get leaded gas, which don't matter anyway because lead was used to cool and lubricate valves and there are no valves in a two stroke.

2. In the winter months in California, they use oxygenated gas, which means they are putting in Etanol (excuse me, my spelling really sucks and Im 38 years old, just get used to it) which is basically Alcohol, so if you run in California in the winter, you will want to get richer cause it will run hotter. I don't know where you are, or if they put ethanol in your 87 octane gas.

3. the lower the octane, the more complete burn of the fuel. Some people will run low octane to pass smog check because it burns faster, which will completly burn all the fuel and less emissions out the tail pipe, higher octane burns slower & you will get ubburnt gases out the tail pipe, so I have been told. for it burning hotter? that is news to me.

 

[ZRT600MtnCat]

If you want to learn about fuel and the characteristics that it posesses, contact a VP Fuel dealer and get the sales brochure, it has a very detailed explaination. Octane is resistance to detonation, there are other aspects of fuel that should be considered as well. I raced a 440 mopar with 11 to 1 and you can not race this without at least 105 octane. But that is a car, VP also sells a race fuel for 2 strokes, which has completely different burn characteristics.

 

[corvette77]

i live as far south in michigan as you can get can damb near throw a rock into indiana the average temp here in the winter season is 25 to 30 degrees F so i guess theres a big diff in the winter temps also i am at sea level the jets on the vmax are a little fat because i will foul a plug from time to time im not saying go out with that old gas and beat the hell out of your sled as you will no doubt have a problem but with fuel prices today do you want to throw your money away and not use the fuel thats in it i never drive it hard frist time out because us old guys have this thing called the rust factor and i myself need to get warmed up some before i go and realy trash the trails  anyway enough said ride on all

 

[machz69]

yeah u need to run higher octain to prevent detonation not only compresion will cause this but also timming advance .