# Octane rating for 2 stroke engines...



## Greg

This subject has been debated on other forums, but I would like to share a first hand personal experience and get the Tractor Forum member's thoughts and comments.

First, for some reason, 2 cycle engines do not like me. The refuse to start easily and run right. I don't know why, but that is the way it has been.

Now as most of you know, I recently purchased a Stihl MS250C chainsaw. The manual states: 

"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" (I am assuming 92 octane).

When I first got the saw, sure enough I had a hell of a time getting it to start. I had fresh fuel (89 octane) with the right mixture of top grade 2 cycle oil. I thought it was just that it was new and not "broken in" yet. I read and re-read the starting instructions in the manual. I watched the video at the Stihl website. Yes, I could finally get it started after about 20 pulls and 30 minutes of hard work. I talked to other people, took it back to the dealer and when they tried it, it started right away. Yep, I was not loved. Finally I rolled all the advice together and got to the point I could start the saw after about 10 pulls. I thought I had reached a new plateau of success and had broken the jinx. I should have stopped there....

I heard, on other forums, that higher octane gas would burn cooler, and I assumed increase the reliability and life of the engine. The Stihl manual even said to use it if necessary. So last week, when I needed more gas, I took my 2 1/2 gal tank to the local gas station, filled with exactly 2 gallons of fresh premium (92 octane) gas, mixed the exact amount of oil, filled the saw's tank and was ready to tackle the logs....

I pulled....

and I pulled...

and pulled...

10 times...20 times...30 times...over about an hours time. I smelled gas (flooded) so I took out the plug, dried it and put it back in.

I pulled...

and I pulled...

and pulled...

I actually got 2 water blisters and 1 blood blister from pulling (with leather gloves on)! Once the starter handle flew back into the saw and clipped my thumb, pinching a nerve. It's still a little numb.

Dog gone it!.......was not what came out of my mouth!

Sooooo...back to the dealer. I talked to my salesman and the service manager. The manager said he sends out all the small engine equipment they sell, not with 89 but with 87 octane gas. He said he would NOT at all recommend premium!

Back to the house, dump the full tank of 92 into my car, and filled up with exactly 2 gallons of 87 octane gas, exact mixture of oil. I dumped the saws gas tank, pumped the primer bulb to flush out the carb, filled the tank with the 87 mix and primed it. I put band-aids on my fingers under my gloves.

Full choke...1 pull...2 pulls, the engine fired once.

Half choke...1 pull...2 pulls, the engine started.

I was born again!!!!

From that time on, I can start that saw fresh with less than 5 pulls, EVERY time! If the saw is warm...2 pulls max!

OK, I am wearing out the leather on my gloves around the knuckle area every time I get ready to saw wood again. I am focusing on making longer pulls on the cord, as opposed to faster, shorter pulls. But I really have to believe the change in octane is my main salvation. I am a sawyer again! (Jason.. (service manager)...who luvs ya?)

Now that's the truth, the whole truth, and nothing but the truth...I swear! (at least I used to).

So what do you guys think?

Greg


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## Live Oak

First off, flush what you read from the manual and heard from the salesman. The last bits of what you wrote were pretty much on point with respect to starting a cold stihl. These are higher compression saws (in case you didn't notice from the blisters :dazed: ) Not to mention that they are jetted LEAN for the tree huggers. If you think your MS250 is a blister maker, try an O-66. :smiles: 

It makes my blood curdle following the instructions on how to start the saw that stihl gives. No way I am starting $900 saw (O-66) cold and letting it rev to max rpm cold! 

Here is what I do. If it is cold outside; I put the saw on FULL choke and pull the rope until it sputters. This may take 2 - 4 pulls......sometimes less. Then I put the choke to the RUN position and pull the rope until it starts or trys to sputter to a start. (1 -3 pulls) If it starts to sputter, be FAST and flip the throttle to keep her runnin'. If it is a little warmer; she usually starts to a steady idle but I flip the throttle anyway to be sure she keeps runnin'. I let my saw idle for a few minutes to let it warm up before putting it to work. If it is warm outside; I put the choke on FULL and SLOWLY pull the rope 3 or 4 pulls to prime the saw and then put the choke in the run position and pull it until it starts. (This may take 2 - 4 pulls.....sometimes more) If it does not start repeat. If your saw is really fussy about cold starts; you may need to adjust the carb. Your owner's manual will cover this. 

I do NOT let the "work bench jocky's" at the store touch your saw. My experience is that they don't give sh!t about it and have no idea what they are doing to it. 

Stihl makes one of the finest chainsaws money can buy and yours may need some adjustment; but yours sounds like mine with respect to cold starts. That is just the nature of the beast. 

As you use the saw more, you will become more accustomed to it. I burn Amoco Premium in mine since day onewith not a single problem. The book calls for 50:1 fuel mix but I mix mine at 40:1 which is cheap insurance and will provide a good fudge factor with respect to rings and bearings. 

I have had my O-66 for about 10 years and she runs like day one. There are "other" ways of starting your saw and folks who don't know much about engine may laugh at my method of starting but your saw will last MUCH longer this way. Do the math on following the book instructions of starting the saw and let it rev to 7,000 rpm cold. Just be patient and easy with her and she will last a life time. :thumbsup:


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## jodyand

I use 87 octane in my weedwacker and blower and it has never took over 5 pulls to start. And my weedwacker is about 5 years old and the blower is 4 years old. I put it on full choke push the primer bulb about 10 times and it always pops by the 3rd pull put it on half choke pull the rope 1 or 2 times and it running let it run on half choke giving it some gas for about a min and put the choke on run and we are off to cut the weeds.
Jody


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## Argee

I go along with that 40:1 ratio being good insurance. And it's pure hippocracy to rev an engine to max RPM if it's a 4 stroke with an oil pump, but I'm not truly convinced it'll hurt a 2 stroke with the oil mixed with the fuel. I've owned a lot of 2 stroke engines and can never remember one getting chewed up from starting it at the recommended throttle.


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## Greg

Chief,

The starting instructions in my manual, and what my salesman told/showed me are essentially the same as you use to start your saw. The exception is going from full choke to "run", bypassing half choke. My salesman showed me how to start it, did it himself then had me do it at the store. I think my initial trouble was just I wasn't used to the saw (and my jinx LOL) and running 89 and then 92 octane gas after I got the saw home. (As I stated above, the saw initially came with 87 from the store but I wasn't aware of that).

My manual says to flip the trigger if in full or half choke to put the throttle in the run/idle position. It says only "open throttle partly - warm up engine for short period", not full RPM.

I guess I'm lucky..my dealer is not a large store (sq. ft wise) but sells a TON of Stihl equipment, especially chainsaws. The sales and service staff are all "into" chainsaws, with many/most owning and using one themselves and have lots of experience. They have answers and tips for all my questions/problems...but it is up to me to let them know my problems or ask the questions. But there's nothing better than tapping onto the experience of the large membership here at the TF for additional help/answers! I have added some oil to my filler tank to bring it to 40:1. Thanks.

Getting back to the octane question, you say you use premium gas with no problems. Does your manual also say it's OK? Do you use from trial/error experience? Have you had problems with lower octane gas? Thanks.

Jodyand,

Same questions of your use of 87 octane gas. 

Argee,

What octane gas do you use? Comments of 87vs 89, 92? Thanks.


It just seems to me, from my experience with different octanes that 87 is the best for my saw.

Greg


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## Ingersoll444

Well, the Chain saws don't realy care, but my old RD400 motorcycle will hardly run at all with 87 gas. Higher octine the better it runs. Granted 60-80 down the road, is a little different then cutting wood.


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## Live Oak

The manual calls for a unleaded or leaded fuel with a minimum of 87 pump octane. It also state to mix Stihl 2 stroke engine oil at 50:1 and other brand mix at 25:1. Oils must be classification TC. DO NOT use BIA or TCW 2 stroke water cooled engine oils


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## Argee

Greg,
I use 87 octane and have never had a problem.

Sure Stihl recommends to use only their oil, what manufacturer wouldn't? It's dollars in their pocket if you use only their product.

I think one of the best marketing cliches of all time was for shampoo. I'm not sure who the manufacturer was, but they doubled their sales of shampoo by adding one word after the instructions.......that word was....REPEAT. Now it isn't always necessary to repeat, but enough people follow the instructions blindly and it makes for great sales.

I guess the moral of the story is, read into what a manufacturer is really trying to tell you. Was "Use only Stihl brand oil" written by the service department or the marketing department?


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## memmurphy

Our Homelite saw originally used leaded gas as well as our oldest Jacobsen mower. The Homelite weed whip is about 15 years old. They seem to run fine on the 87 octane. The saw and weed whip I pull at full choke till they sputter, then set to half choke and they start. If it starts to die when I pull the choke off, I just choke it for a couple more seconds. The old Jake is pushing 40 years old and it may take the better part of a minute at partial choke before it settles down. I just grab whatever oil is available, and if I recall correctly, use 4 ounces/ gallon. :truth: 

The old Jake was run many hours with Quaker State 10w30 mixed in the tank. Guess it didn't hurt it too bad.  

Mark


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## Argee

> _Originally posted by memmurphy _
> *Our Homelite saw originally used leaded gas as well as our oldest Jacobsen mower. The Homelite weed whip is about 15 years old. They seem to run fine on the 87 octane. The saw and weed whip I pull at full choke till they sputter, then set to half choke and they start. If it starts to die when I pull the choke off, I just choke it for a couple more seconds. The old Jake is pushing 40 years old and it may take the better part of a minute at partial choke before it settles down. I just grab whatever oil is available, and if I recall correctly, use 4 ounces/ gallon. :truth:
> 
> The old Jake was run many hours with Quaker State 10w30 mixed in the tank. Guess it didn't hurt it too bad.
> 
> Mark *


A 40 year old saw and still going, that's amazing. And it doesn't care what oil you feed it, as long as you feed it.

As a side note to this ongoing discussion regarding lubricants used in chain saws, I happened to be talking to a couple of grizzled old loggers the other day. I mentioned that I always had trouble keeping the oiler working on my McCullogh saw, and because of this, I went out and purchased a Stihl. They looked at me and laughed (they use only McCullogh, old ones too) and said they used to have that problem but changed to transmission fluid in the chain oilers and haven't had a problem since. That's pretty amazing.


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## Ingersoll444

> _Originally posted by Argee _
> *A 40 year old saw and still going, that's amazing. And it doesn't care what oil you feed it, as long as you feed it.
> 
> As a side note to this ongoing discussion regarding lubricants used in chain saws, I happened to be talking to a couple of grizzled old loggers the other day. I mentioned that I always had trouble keeping the oiler working on my McCullogh saw, and because of this, I went out and purchased a Stihl. They looked at me and laughed (they use only McCullogh, old ones too) and said they used to have that problem but changed to transmission fluid in the chain oilers and haven't had a problem since. That's pretty amazing. *


LOL, Sounds like my dad. He would be late 80's now if he was still with us, and the things he used to do... OMG. 

If he needed oil in something, a chain saw, a tractor, a truck, doesn't matter, he would use what he had. Anything. Got to say, a lot of his stuff was pretty old, so he must have been on to something.


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## jodyand

> _Originally posted by Argee _
> *They looked at me and laughed (they use only McCullogh, old ones too) and said they used to have that problem but changed to transmission fluid in the chain oilers and haven't had a problem since. That's pretty amazing. *


Well yes transmission oil is thinner then motor oil so yes it would work. The way i look at something like that is as long as some kind of oil gets there to lubricate it don't mater what kind of oil but not in the motor. Always use the right oil for the motor dont use transmission oil for motor oil.
Jody


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## Argee

> _Originally posted by jodyand _
> *Well yes transmission oil is thinner then motor oil so yes it would work. The way i look at something like that is as long as some kind of oil gets there to lubricate it don't mater what kind of oil but not in the motor. Always use the right oil for the motor dont use transmission oil for motor oil.
> Jody *


I've purchased bar lube from time to time that was the consistency of motor oil. I think I prefer the thinner stuff as opposed to the STP like oil you sometimes get.


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## memmurphy

We did the motor oil in the gas thing back in the early 70's. One gas can with 2 mowers the other being 4 cycle. We later thought better of guessing the mixture by the amount of smoke and splurged for a second gas can and 2 cycle oil when we bought the chainsaw.

I noticed bar oil is not always the same weight. I've wondered about pouring old motor oil through a screen and using it. But I was afraid it might be a little too thin.

Mark


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## Greg

Thanks for all the replies guys.

Anyone else have any experience, problems with using 87 vs 89 vs 92 gas in their 2 stroke engines?

Greg


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