Octane ? What do you put in your saw?

I think they run better on 93 seem to start a little easier and a little better throttle response. On the very large cuts I also think it keep the rpm up may all be in my head but makes me fill better. (all warm and fuzzy)

Ideally you would want gasoline that contains no ethanol. As far as Octane, I'm really not sure what the advantages would be(that's not to say there are none, I'm sure someone will chime in)

My understanding of Octane is that higher octane fuel will not ignite as quickly as lower octane fuel. It does not contain any more BTU's than lower octane, but the ability of the cylinder to operate at a higher temp(and therefore higher compression) without the fuel autoigniting translates into more power. This makes sense to me in a fuel injected, computer controlled environment, as the computer will know that the fuel is burning stoichometrically and can adjust the fuel and air ratios to achieve maximum power. If gasoline autoignition occurs, the knock sensor will tell the ECU, which will tell the injectors to step down the ignition timing. Higher octane means autoignition will occur at a higher temperature and compression, so the cylinder can operate at higher efficiency and power than lower octane fuel.

All the info I have on this is based on automotive applications; in a small-engine, carburated, 2 stroke application, this could all go right out the window. Maybe the carburetors are pre-tuned to burn 93 octane fuel without premature ignition.

smokinjay said:

I think they run better on 93 seem to start a little easier and a little better throttle response. On the very large cuts I also think it keep the rpm up may all be in my head but makes me fill better. (all warm and fuzzy)

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+ 1 especially the warm and fuzzy part

basswidow said:

yeah - ethanol is bad.

What about if you run 93 - could cause your saw to run hotter or lean? Or is the running lean merely a function of not having the oil mix right?

Do you run 93 in all your 2 stroke equipment? I've just been using 87. Not sure if I need to change that or not?

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running lean would be carb out of adjustment...and yes I run 93 in all my 2 cycles.......93 will not make it run lean or hot!
If the limit caps are in place you will not ever run to lean.

My FIL was having trouble with a few of his saws. When he was at the service center, the guy told him to switch to 91-93. He hasn't any issues since! Based off that, I haven't run less than 91 in any of my small engines.

I only run 93 in my saw. Never any problems. Thats what the dealer said to run in the Husky and it loves it never one carb problem.I also mix synthetic 2 stroke oil with it...... OOO no did i open up a whole can of worms there??

Deere10 said:

I only run 93 in my saw. Never any problems. Thats what the dealer said to run in the Husky and it loves it never one carb problem.I also mix synthetic 2 stroke oil with it...... OOO no did i open up a whole can of worms there??

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lol maybe.....grab your popcorn...

Stoichometrically?????? Whaaaaaaat???

FWIW, I run 93 in anything that has a carb. From my experience, it seems to run better and doesn't go stale as fast as 87.

Ditto on the high octane and definitely avoid Ethanol I'm lucky, one of only two gas stations in the whole country that sell non-ethanol gas is about 8 miles from my house. People will drive from 30 miles away just to get the non-ethanol gas for their 2-stroke and outboard motors (even 4 stroke outboards!!). Ethanol is the small engine and outboard mechanic's friend--a recent story in our local newspaper had an outboard motor repair shop stating that over 70% of their business comes from ethanol problems..........


NP

Octane: http://www.state.mn.us/mn/externalDocs/Commerce/Gasoline_Octane_Facts_102902052227_OctaneFacts.pdf

Octane additives in gas that is mixed with oil, no benefit, actually research shows the opposite.

No more "bang for your buck" to buy high octane for 2 cycle engines.

It does burn slower & run cooler but the additional additives has a tendency to gum up pistons. Regular detergent gasoline is actually better. From some research I read for 2 cycles.

Fill / top off the saw when you are going to use it, (fresh gas) don't fill it & let it set till next time you'll use it.
Keep your mixed gas in a sealed container & as cool as possible. Ever notice how the plastic jugs swell in the sun when out cutting? (my 2-1/2 gallon jug now holds 3 gal)
As soon as you open the container, whoof, some high end are gone. If you smell it, it's flashing off. After 2 months or so of no use, dump the gas out of the saw & put in new .
Empty the tank if your not going to use you saw for a while.

My buddy was a lab tech of the Tesoro refinery here, told me unless it's a high performance sports car engine, waste of money. Fresh gasoline is more important.

Peter SWNH said:

FWIW, I run 93 in anything that has a carb. From my experience, it seems to run better and doesn't go stale as fast as 87.

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A buddy of mine who runs a motorcycle/ATV repair shop told me that gas loses octane when it sits in storage, so it is prolly a good idea to start with a higher octane gas. He strongly recommended 93 octane + stabil+ octane boost for 2-stroke applications.

bogydave said:

Octane: http://www.state.mn.us/mn/externalDocs/Commerce/Gasoline_Octane_Facts_102902052227_OctaneFacts.pdf

Octane additives in gas that is mixed with oil, no benefit, actually research shows the opposite.

No more "bang for your buck" to buy high octane for 2 cycle engines.

It does burn slower & run cooler but the additional additives has a tendency to gum up pistons. Regular detergent gasoline is actually better. From some research I read for 2 cycles.

Fill / top off the saw when you are going to use it, (fresh gas) don't fill it & let it set till next time you'll use it.
Keep your mixed gas in a sealed container & as cool as possible. Ever notice how the plastic jugs swell in the sun when out cutting? (my 2-1/2 gallon jug now holds 3 gal)
As soon as you open the container, whoof, some high end are gone. If you smell it, it's flashing off. After 2 months or so of no use, dump the gas out of the saw & put in new .
Empty the tank if your not going to use you saw for a while.

My buddy was a lab tech of the Tesoro refinery here, told me unless it's a high performance sports car engine, waste of money. Fresh gasoline is more important.

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I guess they should contact stihl husky and dolmar I pretty darn sure they all call for at least 89-91 in the Manuel + it makes me fill better. (all warm and fuzzy)

Lot's of fancy answers....all I can say is that I run 87 in my MS 310. She starts fine, runs great and she cuts wood. I like high octane beer, does that count for anything?

stee6043 said:

Lot's of fancy answers....all I can say is that I run 87 in my MS 310. She starts fine, runs great and she cuts wood. I like high octane beer, does that count for anything?

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yep as long as your getting the warm and fuzy part... but for real sthil has moved there min. octane rate to 91. I have more in my saws than trunk and the saws dont eat much so I run the 93... and there is some who run 100

smokinjay said:

stee6043 said:

Lot's of fancy answers....all I can say is that I run 87 in my MS 310. She starts fine, runs great and she cuts wood. I like high octane beer, does that count for anything?

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yep as long as your getting the warm and fuzy part... but for real sthil has moved there min. octane rate to 91. I have more in my saws than trunk and the saws dont eat much so I run the 93... and there is some who run 100

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I wondered why the Stihl manual said to run mid-grade fuel. Don't remember where I read it but leaned that the oil lowers the octane to the point where detonation can occur and ruin the saw. It sounds plausible so I am running high test to be safe. Since I'm only cutting firewood for myself I don't go thru that much fuel anyway.

You need to run what the MFG states in the manual I think Stihl says 89. Since octane is only a figure used to express the resistance to detonation running anything higher than what's needed is a total waste of money. The oil companies have long tried to promote the higher grades ..... guess why more profits.
Fresh gas makes a difference and the chemicals like Stabil and Sea-foam do help to preserve the gas.
Just so you don't think I making this up I got the info from my BIL who has been a chemical engineer for Shell oil or whatever they are called now for the last 20 years. With modern cars it's even a little different , if the MFG says premium required vs recommended . Because the computer will adjust the timing the car "recommended" will run fine with regular with a little reduction in performance on full acceleration on the other hand the "required" car will probably suffer detonation on regular gas.

Right now im runnin some VP 96 octane that was leftover from my bro-inlaws bike. The VP and motul race mix makes em run like ***** apes! Plus the smell is just awsome haha.

One of my Stihl manuals says at least 87, not sure if I can get the good stuff around here close, I have cut wood for over 30 years and not followed all the rules(gas is stored longer than recomended) but have never had a gas problem (rather be luckly that good).

Tony H said:

You need to run what the MFG states in the manual I think Stihl says 89. Since octane is only a figure used to express the resistance to detonation running anything higher than what's needed is a total waste of money. The oil companies have long tried to promote the higher grades ..... guess why more profits.
Fresh gas makes a difference and the chemicals like Stabil and Sea-foam do help to preserve the gas.
Just so you don't think I making this up I got the info from my BIL who has been a chemical engineer for Shell oil or whatever they are called now for the last 20 years. With modern cars it's even a little different , if the MFG says premium required vs recommended . Because the computer will adjust the timing the car "recommended" will run fine with regular with a little reduction in performance on full acceleration on the other hand the "required" car will probably suffer detonation on regular gas.

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Some motors are set up to run high octane, i.e. my Corolla XRS has a high-performance Celica GT-S engine that require 93 octane or higher fuel as stated in the manual. My other Toyota (Tacoma) gets regular and runs just fine on that.

That being said, given the high-revving nature of 2-strokes and the fact that most people run their saw either idling or at wide-open throttle, I think it makes sense to provide the best fuel that I can. Seeing as we're talking about a $.10 difference every time I mix up a gallon of chainsaw fuel, it really seems to be a no-brainer to use the higher octane fuel.


NP

Okay, so I have a gallon of old (stale) fuel mix. How do you dispose of it?

DanCorcoran said:

Okay, so I have a gallon of old (stale) fuel mix. How do you dispose of it?

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I use old gas and oil to fuel my burn pile.