Octane

[Incomplete]

Hi guys!

Me again, with my ignorance showing.

I wasn't raised to use high octane in anything. And in fact, I still don't, too cheap (poor) to justify the extra expense. However I want to do right by my tools because I want them to last a lifetime

Is there any real advantage in using high octane fuel in chainsaws? And why? What is the science?

If you have the facts, please present them. If you only have anecdote and "thats how my PawPaw did it" please hold them until after the Teachers have schooled us.

My anecdotal evidence is this: when I bought my Echo CS-341 the store owner said that I MUST MUST us high octane fuel and to that extent he filled the saw and started it in the back room before sending me on my way. The first job I did, my apple pruning in March, I pulled the saw out and fired it up; eventually. When it did finally run, it ran like crap, was finicky under moderate load, and would not idle. I was sick. Because I had done my research and been helped by you all and had made the best decision possible, and the saw was acting like a dud. I ran it dry, grumbling the whole while. I refilled the oil and the fuel with my low octane mix, and the little baby fired right up and ran like a champ and has continued to purr like a kitten. This is the same fuel I have been using in my Swedish box-store Husky with no noticeable ill effects. So this raised the question, if high octane is so good for chainsaws, then why did my saw run better on the bottom shelf?

 

[Gologit]

How long did the high octane fuel from the dealer stay in your saw?

 

[CTYank]

Ditto there's much more working here than simply fuel octane rating.

And ... production chainsaws' compression ratios are such that 87-89 octane (avg. of research + motor) is plenty. These things survive on mexican gas! (Old joke.)

The more oil you mix in, the lower the actual octane of the mix, and sustained running @WOT and low load, as in the way some do limbing requires higher octane. Detonation eats piston crowns, and it's hard to detect @WOT and low load. (Better yet, don't do that!)

Store fuel only in cool, dry places, in sealed containers. Since you can't ensure the last part in the saw's tank, run it dry first. Or run it often. Whenever possible, shake up the mix before fueling or cranking.

Life sometimes throws you a curve, and you gotta deal with it. Assume nothing.

 

[Incomplete]

How long did the high octane fuel from the dealer stay in your saw?

Only a couple of weeks TOPS

 

[Incomplete]

Ditto there's much more working here than simply fuel octane rating.

And ... production chainsaws' compression ratios are such that 87-89 octane (avg. of research + motor) is plenty. These things survive on mexican gas! (Old joke.)

The more oil you mix in, the lower the actual octane of the mix, and sustained running @WOT and low load, as in the way some do limbing requires higher octane. Detonation eats piston crowns, and it's hard to detect @WOT and low load. (Better yet, don't do that!)
.

What is @WOT? Can I play with fuel mixture leanness without fear of fouling the motors? What is the specific necessity of the oil mixture? Obviously it's a must but it's something I've curiously never questioned till now.

 

[TonyRumore]

I don't know about 2 strokes, but I have been drag racing motorcyles since the 80's and found that running higher octane than your motor needs, reduces engine power and makes the engine hard to start. Some of the worst passes I have ever made, were with high octane race gas in a motor that didn't need it. The bikes generally make the most power with the lowest octane fuel that doesn't cause pre-ignition detonation.

 

[tdi-rick]

One simple reason that high octane is recommended for OPE on this side of the Pacific is that it doesn't contain any ethanol, so people won't have an issue if they leave it sitting for six months (which they will do, regardless of what they are told)

FWIW, if you are going to leave fuel in a container for months on end it's preferable to use steel.

HDPE containers are actually porous to the aromatic portions of fuel, they pass clean through the walls of the container over a period of a few months dropping your fuels octane and buggering up the burn characteristics.

[edit] I should have added that what I'm calling high octane is 98RON pump fuel, which I think is equivalent to US 93AKI ??

 

[Incomplete]

I don't know about 2 strokes, but I have been drag racing motorcyles since the 80's and found that running higher octane than your motor needs, reduces engine power and makes the engine hard to start. Some of the worst passes I have ever made, were with high octane race gas in a motor that didn't need it. The bikes generally make the most power with the lowest octane fuel that doesn't cause pre-ignition detonation.

This is good to know because I've been riding bikes my whole life and again, used cheap fuel with NO adverse effects, until recently when people I trusted insisted that the CBR be run on nothing less than the most expensive.

 

[Incomplete]

FWIW, if you are going to leave fuel in a container for months on end it's preferable to use steel.
??

Jerry cans, baby!

 

[BrocLuno]

This has been asked quite a bit lately. Stock saw will run fine 95%of the time on Regular. Those times when it won't you'll know ahead of time. Maybe a really hot day at say 110* and dry as parchment. Working a fire line when the air temp is way up. Otherwise, lowest grade your motor will handle is best. Least additives mean cleaner combustion.

High octane slows the flame front, but this can affect port timing, lead to excess flame in the exhaust port at high speed which will hurt things.

There must be enough oil to do the job. Spend your money on oil, not gas. Oil is what does the lubricating and there ain't much in there, even at 40:1. I suggest EGD/API-TC oils rated for air cooled two strokes. Do not use TCW3 outboard oil as it is not designed for the operating temps of air cooled motors.

Keep the chain sharp and keep a load on it when the throttle is open. WOT means Wide Open Throttle.

 

[tdi-rick]

Jerry cans, baby!

Yep

 

[tdi-rick]

[snip]
Least additives mean cleaner combustion.

Not necessarily.

The high octane fuels marketed by Shell, Caltex and BP here are claimed to lead to cleaner burning/less deposits in the chamber.

High octane slows the flame front, but this can affect port timing, lead to excess flame in the exhaust port at high speed which will hurt things.

Old wives tale.

High octane race fuels can actually have faster flame propagation than regular fuels, they just resist spontaneous detonation at higher than normal cylinder pressures.

Think how fast the flame front needs to travel at the high revs of a racing two or four stroke.
Fast burning race fuels can help pull spark out of an engine, leading to more power.

 

[Nitroman]

Weeeellll...I have used the (Oh MY GOD!!!!), avgas 100LL in my outboards (88hp Evinrude, 175hp Johnson), snogo's (1994 Polaris Sport 440, 1997 Polaris Ultra SPX SE, 1999 Polaris 800 XCR, 2000 Polaris 800 XCR, Arctic Cat 570 Bearcat), and chainsaws (Husky 137, 394 and 3120). Only the 3120 really needs it as it has been thoroughly massaged.

But they all ran excellently and I had no probs with anything except when it get below 0* F, the snogo's would take a few more turns of the crank to go.

The gas you had from the dealer was bad.

Run what you want and be happy.

 

[Vibes]

I've brought this question up many times, and haven't got a real good answer so I'll ask it here while I have the gas experts attentions. I've been buying regular 87 octane, and adding the measured amounts of octane boost. My reason is because the 93 and 91 octane thats in the tanks at the stations has been in these tanks for an awfully long time, because car drivers really don't use it anymore. When the store owner buys Hightest, he's only getting a minimum amount so its being mixed in there tanks with old crappy gas.

Are these octane boosters good or bad for my saws? I also agree with the sealed containers if gas needs to be stored more than 5 days. I'm using gallon wine bottles these days if I have to keep fuel.

 

[CTYank]

What is @WOT? Can I play with fuel mixture leanness without fear of fouling the motors? What is the specific necessity of the oil mixture? Obviously it's a must but it's something I've curiously never questioned till now.

Interesting statement of questions, to say the least. First should be obvious, and has been answered.

"Play with fuel mixture leanness"? Not advisable, unless you know what you're doing- easy way to melt pistons, mucking about with high-speed mixture. See Brad Snelling's video on YouTube about how to set that, with none of the tach BS. Assuming you can tell the difference between 2-stroking and 4-stroking of 2-stroke engine. (Fouling a plug is nothing compared to melting a piston crown.)

"Necessity of oil mixture"? Seriously? To minimize metal-to-metal with rapidly moving engine innards, for one. Best bet is to use mix ratio on oil container, since additional oil reduces octane rating, and promotes deposits which can flake off and score piston/cyl. or start forest fires. Exception: keep it <= 50:1. Forget 100:1.

 

[Fish]

The weather is too nice out for a full blown octane war!

 

[Incomplete]

The light bulb has come on: no oil reservoir therefor need oil for lubricant. Duhh!

 

[Incomplete]

Weeeellll...I have used the (Oh MY GOD!!!!), avgas 100LL in my outboards (88hp Evinrude, 175hp Johnson), snogo's (1994 Polaris Sport 440, 1997 Polaris Ultra SPX SE, 1999 Polaris 800 XCR, 2000 Polaris 800 XCR, Arctic Cat 570 Bearcat), and chainsaws (Husky 137, 394 and 3120). Only the 3120 really needs it as it has been thoroughly massaged.

But they all ran excellently and I had no probs with anything except when it get below 0* F, the snogo's would take a few more turns of the crank to go.

The gas you had from the dealer was bad.

Run what you want and be happy.

Just saw that avgas has lead into! Curse You Hypocritical EPA!!!!! Can you send me some? Sounds like good stuff ;oP!

 

[Eecho]

The dealer told you thid due to ethanol in todays fuels . The ethanol draws moisture and isnt any good for the minumum octane needed by the manufacturer to feel comfortable to not see any adverse effects from it . Basically if you use 87 it burns hotter in the combustion chamber then 93 . The manufacturers see that people buy crap mix oil and if the ethanol in the fuel draws moisture that can cause scoring easily in combination. The fuel companys add ethanol to fuel to increase its octane from 84 octane to get it to 87 nowadays but if it phase seperates it will go back to 84 and be lower quality then manufacturers like , combine that with poor mix and the epa saying less mix in the air then you have problems . Just use a high quality synthetic and make sure you use a air tight container combined with no longer then thirty days storage and you should be fine . I buy non ethanol fuel and high quality synthetic mix oil for better dispersion throughout the fuel.

 

[awspence]

The only ethanol free fuel available in my area is 93 octane, so that makes my decision to run high test easy. If i could by ethanol free 87, i would most likely not bother with high test.