Gas Octane??

[kevinj]

Which is the best grade of fuel?
I've heard in the past that mid-grade (89 octane) was better than the others, (87 or 92), because, there was another ingredient in it that the others didn't have. If this is this correct, maybe someone can explain why it makes a difference.
Again, Thanks for your responses.

 

[Pablo26]

I have good luck with nothing but super, here it is 91 currently. Try to get it without methanol if possible.

 

[gslater]

Not sure what's "best", or even what that means, but I do know that the manual for my new Stihl 361 recommends mid-grade (89) gas.

 

[Butch(OH)]

The best would be the Mfg recommended grade. Contrary to popular belief there is no HP benefit from running octane higher than is needed to prevent detonation. My two newest saws, Echo and a Sindiawa say up to 10 percent alky in the fuel is Ok, the older manuals say no. Since I have one can of mix for all saws it contains no alky 89 and my favorite oil at recommended ratios

 

[Bob Wright]

The reason for "no alky" for older Echo's is the fuel will eat the gas lines, they will look like melted rubber fishing worms and some of them are real hard to find now....Bob

 

[blis]

i just use premium for all my saws and motorcycles...

 

[PES+]

Just a point of fact

MBTE is methanol so if you can find gas without it or Ethanol I'd like to know where

 

[Monkeyhanger]

MBTE is methanol so if you can find gas without it or Ethanol I'd like to know where

Hi,

MBTE or more correctly MTBE is "methyl t-butyl ether" or "2-Methoxy-2-methylpropane" as it is also known (C5H12O) not methanol (CH3OH). It is an anti knock compound used in place of lead. Methanol is one of the ingredients used to make MTBE though.

Anyway here in Europe I use 95 octane "Super" for my saws and car but 91 octane "Normal" for my motorcycle.

Bye

 

[PES+]

Okay

I'll let you tell me why methanol is not good in a saw and then tell me how MBTE does not cause these same problems. Also please enlighten me as to these other voodoo ingredients that are in MBTE other than methanol

 

[PES+]

Theory and actual prodoct on the market are worlds apart. The very reasons for the owners manual cautions against alcohol blends holds true for all MBTE fuels I have used and mixed here. I have witnessed batches of hi test fuel here that almost completely allow the 2 stroke oil mix seperate out and for the last 10 years have yet to find a gasoline for road use that does not attack both natural rubber and neoprene blends for fuel system components

 

[Monkeyhanger]

Theory and actual prodoct on the market are worlds apart...

Hi,

you're mixing things up a bit. Again MTBE is not methanol. Fuel can have both MTBE and methanol in it or MTBE and ethanol or ETBE and methanol etc. etc. That still does not change the fact that MTBE is not methanol! It really is that simple.

Anyway MTBE is made from methanol and isobuten, in other words a different substance with different properties. As far as I know neither MTBE or ETBE are agressive to plastics or rubber. However it seems that methanol and ethanol are somewhat aggressive.

For you to say that MTBE is methanol and then to say that "theory" has nothing to do with actual products doesn't make much sense to me. Since fuel can contain both then that is probably the reason why you are mixing the names up a bit.

Anyway I've been using Euro super which contains roughly 3% - 5% MTBE for 4 years in my 460 and not a single problem to date. Superplus contains 10% - 15% MTBE and my friend has used it in his SOLO 651 for 5 years without a problem. He even uses 1 year old mix with no problems whatsoever. However our fuels don't contain much if any methanol or ethanol. Yet...

Bye

 

[BostonBull]

Let me take a stab at this....I most likely am worng.

Methanol is not good in a saw because it attaches itself to the Hydrogen Atoms (Water) and settles on the bottom of the tank. Not bad but the fuel pick-up is in the bottom of tha tank so the first thing in is pure Methanol and Hydrogen. (alcohol and water)

MTBE is what they use instead of lead to help raise the Octane of the fuel chemically. BUT they are trying to get away from using it because of the extremely toxic properties to ground water. Aslo there is a chemical process which adds oxygen to the combustion chamber which makes the saws run leaner because the oxygen is being added chemically instead of through the air.

This is just what I remeber from my classes, off my notes too. Could be wrong.

 

[1wildthing]

methanol does not "attach" to the water, it absorbs water, and allows it to be burned in the engine. MTBE, methanol, and ethanol are all added to gasoline for the same reason. To oxygenate the fuel. This results is fewer emissions. Methanol and Ethanol are also essentially the same thing. They are both alchohol. Ethanol is grain alchohol, while methanol is wood alchohol. MTBE is being discontinued due to pollution concerns, so eventually alchohol will be everywhere. (at least in the states) The only concern it has is that it may degrade some rubbers and plastics, but at 10% doesn't seem to hurt any cars, so I would imagine that saws would be okay too.

 

[thomas72]

Actually I would not think methanol would absorb water. I think it will bond to water, due to the fact methanol a type of alcohol and is bonded with a hydrogen bond. Therefor methanol will bond with water because hydrogen bonding is stronger than Covalent and Dipole Dipole.

 

[BostonBull]

Actually I would not think methanol would absorb water. I think it will bond to water, due to the fact methanol a type of alcohol and is bonded with a hydrogen bond. Therefor methanol will bond with water because hydrogen bonding is stronger than Covalent and Dipole Dipole.

Thats what I was always taught too....but I dont have a VAST knowledge to back it up.

 

[1wildthing]

HEET or gas line antifreeze is usually 100% methanol. Look at the warning labels and such. It is not bonding chemically. It is dissolving the water, just like salt will dissolve in a glass of water. The alchohol then allows the water to mix with the gas, and the water in the tank is essentially gone.

 

[BostonBull]

Cool fact we learned in Silver school that most of you gurus already know I am sure.

The E-85 gas CANT be run in saws. Physically. The Ethanol content is so high, and ethanol is so thick it wont fit through the passages and jets in the carbs we use on saws.

Takea small graduated beaker with a lid on it and pour some 2 stroke MIXED E-85 ga in it and let it seperate. It will be gas on top, then ethanol then water. The Ethanol looks like a giant snot/lungy. Very gross to look at. When in carbs it comes out of the passages, welch plugs, and jets in long gross strings.

One more cool fact....

You know the test pastes such as Aqua Check to check for water in fuel? It wont read correctly if using Stihl Ultra oil. Something about how the Oil is made makes it test negative even if there is water. I forget the whole story but...

 

[Canyon Angler]

I think 1wildthing is right...grain alcohol and wood alcohol are just solvents that make water soluble in gasoline. Without alcohol the water and gasoline will be like oil and vinegar...they will never mix. The alcohol allows them to mix without separating. Even though water is not soluble in gasoline, and gasoline is not soluble in water, both of them are soluble in alcohol, which makes them all able to mix homogeneously.

For more, see: http://en.wikipedia.org/wiki/Miscible

Oh yeah -- on the methanol thing: I've seen on the labels that you should NEVER use methanol (methyl alcohol or wood alcohol) in a 2-stroke engine. I don't know why but I suspect that methanol is such a strong solvent that it could theoretically wash away the oil on the cylinder walls and cause a seize.

 

[BostonBull]

HEET or gas line antifreeze is usually 100% methanol. Look at the warning labels and such. It is not bonding chemically. It is dissolving the water, just like salt will dissolve in a glass of water. The alchohol then allows the water to mix with the gas, and the water in the tank is essentially gone.

Thats a good thing...but use too much and you get phase seperation. Which willpull the water and methanol/ethanol out of the fuel and it will sit in the bottom of the tank right near the fuel picku-up. This is why gas stations pump intakes are up off the bottom of their tanks...sometimes by a couple of feet.

 

[BostonBull]

I think 1wildthing is right...grain alcohol and wood alcohol are just solvents that make water soluble in gasoline. Without alcohol the water and gasoline will be like oil and vinegar...they will never mix. The alcohol allows them to mix without separating. Even though water is not soluble in gasoline, and gasoline is not soluble in water, both of them are soluble in alcohol, which makes them all able to mix homogeneously.

For more, see: http://en.wikipedia.org/wiki/Miscible

Oh yeah -- on the methanol thing: I've seen on the labels that you should NEVER use methanol (methyl alcohol or wood alcohol) in a 2-stroke engine. I don't know why but I suspect that methanol is such a strong solvent that it could theoretically wash away the oil on the cylinder walls and cause a seize.

This is copied from above link....

In organic compounds, the length of the carbon chain often determines miscibility relative to members of the homologous series. For example, in the alcohols, ethanol has two carbon atoms and is miscible with water, whereas octanol has eight carbon atoms and is not miscible with water. Octanol's immiscibility leads it to be used as a standard for partition equilibria. This is also the case with lipids, the very long carbon chains of lipids cause them to almost always be immiscible with water.

I *THINK* that the reason these two dissolve in the gas is becasue the Hydrogen Atoms combine, and attach together. Ocatanol has 8 carbon stations and EIGHTEEN Hydrogen stations. As stated before Hydrogen to Hydrogn is a great bond.