Ethanol/octane question

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Applesister

Minister of Fire
Dec 5, 2012
2,483
Upstate NY
Found ethanol free 91 octane at a local station.
Sent pic to my sister who told me that her maintenance guys at her work said not to use high octane fuel in chainsaws.
Im all excited to have a local company offering the option.
I plan on using this fuel for all off road equipment including an old tractor that runs on gas.
For splitter, chainsaws, weedeaters, leaf vac, mowers..etc..
Will the 91 octane run the saws hot? Any worse than the ethanol fuel?
20150424_164630.jpg
 
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We have 93 octane ethanol free at one station in town. That is all i use in all my power equipment. I also use startron in it too. Ive been using this gas in all my power equipment almost 15 years, since i bought my first 4wheeler. I have never once had a carb problem or any other gas related problems. Thats the honest truth too.
 
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Is startron a fuel additive or a complete product?
The local saw dealer told me that fuel stabilizers are mixed into the oil additive so I never "conditioned" chainsaw fuel.
I do on the tractor though, a Continental gas engine was designed to run on leaded gas, not ethanol laced gas. I know its not a race car but...
 
Everyone I know who sells and services in our area always say to use premium (higher octane) gas. Since we can't buy non-ethanol in our area that I know of, it might make a difference without the ethanol but I see no reason that using a higher octane would cause any harm. What were his reasons for not using it?
 
I think you got some bad advice.

Applesister said:
Will the 91 octane run the saws hot?
Click to expand...

Quite the opposite. Here's what the owner's manual for the MS260 (just picked a model at random) has to say on the subject:

Use mid-grade unleaded gasoline with a
minimum octane rating of 89 (R+M/2). If
the octane rating of the mid-grade
gasoline in your area is lower, use
premium unleaded fuel.
Fuel with a lower octane rating may
increase engine temperatures. This, in
turn, increases the risk of piston seizure
and damage to the engine.

So, they're concerned about the octane being too low, not too high.
 
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That is what I use.
 
Startron is fuel additive. It helps with the ethanol issue and stabilizes fuel for 2 years. 1 oz treats 5 gallon and after everything has been treated, 1 oz for 6 gal. I put 1 oz in my 5gal jug and 1oz in 2gal jug that is for my chainsaws. Apparently its pretty potent stuff. I have excellent luck with all my stuff.
 
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I use ethanol free 91 in my small engines, except the lawnmower which is my red headed step child of small engines. It gets the old gas, 2 cycle and not. Well, that's not true, the chipper burns so much oil (always has) that I put used motor oil in it. I guess that's the true b*tch of the small engines.

I've seen the ethanol free pop up more and more up here. It's 100X more available than it was 3 or 4 years ago. I'm thrilled and can't wait until the stations start carrying it in mid grade, and eventually in the 87 octane. Ethanol should be left to stuff we drink.
 
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The higher the octane the more resistant it is to pre-ignition (detonation) and the slower it will ignite. You will make the most power using the lowest octane which WILL NOT detonate. Higher octane will help in those instances where you have high compression and/or aggressive fueling/timing which are prone to detonation. Although I don't think this is an issue with chainsaw motors. I solely use high octane fuel in our small engines as it's the only fuel around here w/o ethanol and is the only reason why I use it. If I could find non-ethanol 87 octane I'd be using that.
 
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[quote="DougA, post: What were his reasons for not using it?[/quote]
Its 3rd party information to start, I wasnt able to ask. The 2 mechanics that I pay to do garage work say to use the 89/91 octane.
My question was whether higher octanes cause engines to run "hot" in chainsaws.
It might be because Im not that strong that chainsaws seem to be under high compression. Because pull starting some of them isnt easy.
But Im reading here...
 
DougA said:
What were his reasons for not using it?
Click to expand...

Its 3rd party information to start, I wasnt able to ask. The 2 mechanics that I pay to do garage work say to use the 89/91 octane.

My question was whether higher octanes cause engines to run "hot" in chainsaws.

It might be because Im not that strong that chainsaws seem to be under high compression. Because pull starting some of them isnt easy.

But Im reading here...
 
Thanks for all your info everyone.
So this is what Im understanding: Octane doesnt bear on making engines run hotter.
If chainsaws are high compression then higher octane is better. Lower octane causes faster ignition. (Engine knocking and dieseling)
It would be best to consult owners manuals on fuel recommendations. Good idea...duh...
It was surprising that higher octane causes slower ignition allowing more compression before ignition(not what I would think) But now I understand the relationship of high octane/high performance.
Running hot is others issues, in simple terms...plugged air filters etc.
I have several thoughts on this as it applies to several different types of equipment.
One question is older chainsaws (pre ethanol era) and older tractors(pre unleaded gas era)
Please correct me on any of this if Im heading down an ignorant path.
 
JRHAWK9 said:
The higher the octane the more resistant it is to pre-ignition (detonation) and the slower it will ignite. You will make the most power using the lowest octane which WILL NOT detonate. Higher octane will help in those instances where you have high compression and/or aggressive fueling/timing which are prone to detonation. Although I don't think this is an issue with chainsaw motors. I solely use high octane fuel in our small engines as it's the only fuel around here w/o ethanol and is the only reason why I use it. If I could find non-ethanol 87 octane I'd be using that.
Click to expand...
Great info...thanks!!
 
Jon1270 said:
Here's what the owner's manual for the MS260 (just picked a model at random) has to say on the subject:

Use mid-grade unleaded gasoline with a
minimum octane rating of 89 (R+M/2). If
the octane rating of the mid-grade
gasoline in your area is lower, use
premium unleaded fuel.
Fuel with a lower octane rating may
increase engine temperatures. This, in
turn, increases the risk of piston seizure
and damage to the engine.

So, they're concerned about the octane being too low, not too high.
Click to expand...
Can you get owners manuals on older chainsaws if you no longer have one?
I have an 029 super fairly old.
 
Pre unleaded gas vehicles can wear faster due to less lubrication. Valve guides are the place usually mentioned. Hardened seats can be installed to counteract this.

I imagine Stihl keeps their compression ratios about the same. Maybe somebody has a manual on it, but I'd expect one from a 290 would be about the same. I use the 91 without ethanol in my 290 and other Stihl equipment without any issues.
 
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I found a manual for my 20+ years old Stihl 026 on line at the official Stihl site. I have a Husky on order, actually expected to see it last Friday, and have been reading a copy of the owner's manual that I found on line so I could be ready to go with my new toy. These days owner's manuals for anything that costs more than $100, not just saws, seem to be readily available on line.
 
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I will look for a manual for the 029.
Thanks again guys.
Also I ran all this by my brother and one of my mechanics and they both agreed with jrhawk9 post. Very interesting info for me.
Now I understand how the lower octanes dont really work in performance vehicles/equipment.
And one more thing, my mechanic brought out my Stihl catalog and showed me the can of premixed fuel they sell which has 92 octane. The Stihl Motomix.
Which I would never buy because they are just pricey items for me.
$3.07 for E free higher grade fuel is ....a little late in coming but SO happy to finally see it.
 
In the odd case than an old Stihl owner's manual isn't available as a PDF, Stihl will actually mail you a paper copy for free. I got a photocopied 034 manual that way a couple of years ago.
 
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