octane of gas in mix????????

[whitearrow]

​

whatup fellas,
this is my first post here so please be patient with me if this has been covered before.i am the proud owner of a stihl ms 260 pro.i have been running it pretty extensively in the past couple of months courtesy of hurricane katrina.i had about 15 beautiful hardwoods down at my farm.anyway back to my question,what octane do you guys use in your stihl chainsaws?i was just reading my manual and it said that i should use only 89 or above octane in my mix for my saw.i have been running 87 for a month or so,before i read that.do you guys think that i have damaged my engine in any way?it says in the owners manual that any octane rating of below 89 will increase the temperature in the engine and could lead to piston seizure and damage to the engine.anyway what do you guys use in your stihl saws?hope that i didn't damage anything,i really like my 260 pro.
whitearrow->>>----------------->​

 

[davefr]

Yes, this question has been answered at least 10,000 times.

That's why there's this wonderful feature called SEARCH.

I prefer fresh premium octane fuel but I doubt regular would hurt your saw.

 

[smcowboy1974]

In most of my stihl's or for that matter all of my saws I use 92 octane or higher with 32:1 mix of Mobil racing 2T or Citgo aircooled semi synthetic. This way your stihl should last you a long long time!

 

[tony marks]

what snocowboy said

 

[WRW]

I hate to admit this, but I ran 87 until I had cut around 90 cords of wood, then read the manual and started using 89. Didn't seem to hurt my saw any, but I won't go back to 87.

Since it was brought up...I use 50:1 on a consumer grade saw and it is still cutting like a champ.

 

[West Texas]

Premium gas with 40:1 ratio using good grade oil. The extra cost for good gas and good oil is not that great and IMHO it insures the safety and performance of the saw. Now if I could find a comparable formulae for me the operator, that would be truly great.

 

[DeanBrown3D]

West Texas - why do you use 40:1?

 

[West Texas]

There has been an exhaustive discussion on this subject from time to time. The ratio varies from 100:1 for synthetics to 32:1 for some of the pros who are in the field all day. After having read all the pros and cons on the subject, I concluded that the best compromise for me was 40:1 and I'm satisfied with the results, after initially running 50:1 in my saws and weed eaters. Do a search on this AS and you will get scads of technical, common sense and pure BS on this subject. Then do what you think is best.

 

[WadePatton]

I always buy the highest octane available at the pumps for my small equipment. If 87 is 1.29 and 91 is 2.59--well darn it costed me 1.30 xtry to get a gallon of the good stuff. That's the price of a soda-POP.

Ratio--well I've just gone to 32:1 because my new saw tech said so. 50:1 has served me well for years, but he has convinced me otherwise. He also runs 110 octane. Lot easier to add oil than to find racing gas.

Pick something and be happy with it. I SERIOUSLY doubt that 87 octane has ever killed a saw, but I'm not saying you can't make it happen. I just don't run my stuff that hard.

 

[RES]

I don't understand why Octane should be a factor in a 2-cycle engine. My understanding is that additives that increase the Octane of the gas are added to the gas to prevent pre-ignition or knocking. This is not a problem with 2-cycle engines or am I missing something.

 

[IndyIan]

RES,
I think you are getting confused with diesel engines, preignition in your saw will end its life pretty fast... Holed pistons or bearing failures.
There are 2 stroke diesels as well but not found in modern chainsaws....

What I have read somewhere though is that the octane of your mixed gas is quite a bit lower than straight gas. Obviously the manufactures take this into account.
Ian

 

[Lakeside53]

RES,
I think you are getting confused with diesel engines, preignition in your saw will end its life pretty fast... Holed pistons or bearing failures.
There are 2 stroke diesels as well but not found in modern chainsaws....

What I have read somewhere though is that the octane of your mixed gas is quite a bit lower than straight gas. Obviously the manufactures take this into account.
Ian

...and it rapidly decreases with storage, so start higther...

 

[WadePatton]

...and some saws are running more compression than OEM spec.

 

[Bad E]

I run the highest available octane in my 2 strokes.

 

[1953greg]

correct me if im wrong but dosent the added oil increase octane. higher octane means higher flash point. and the oil definitely has a higher flash point. right?

good day 1953greg

 

[RES]

So what you are saying is that pre-ignition occurs in a 2-stroke chainsaw as well as in a typical 4-stroke engine. That makes sense. Can you tell when pre-ignition occurs? What is the compression ratio of a typical chain saw?

 

[timberwolf]

New stock saws run about 160 PSI, due to the small piston size of a 50cc saw and high RPM it is amazing just how high the compression can be run on 87 oct pump gas.

 

[WadePatton]

So what you are saying is that pre-ignition occurs in a 2-stroke chainsaw as well as in a typical 4-stroke engine. That makes sense. Can you tell when pre-ignition occurs? What is the compression ratio of a typical chain saw?

Sure it makes sense. Compressing air/fuel and igniting with spark--no different that a 4-cycle.

Funny how we talk about compression ratios in 4-cycle and PSI in 2-strokes. The feller I know using very high octane has saws making 200 psi. I doubt they'd make it on 87.

 

[Kneejerk Bombas]

Anyone ever do timed cut comparisons with the same saw and wood, and only change the octane of the fuel?
Would it cut that much faster that it is worth the extra buck or two per can of gas?

 

[lesorubcheek]

Mike its my understanding that higher octane provides one benefit and only one which is to prevent predetonation at higher compression. So, if an engine is running normally without predetonation on say 87 octane gas, then using 92 octane will add zero benefit. If however your engine is predetonating, then without a higher octane gas you'll be shortening the life of your engine. Every engine is designed with different requirements based upon compression ratio and ignition timing.

I know people that put premium gas in their normal run-of-the mill cars with the logic that it gives them more power. I never even try to convince them that its money down the drain with no added benefit. Now maybe I'm wrong and someone needs to straighten me out, but I'm a firm believer that this is the way it works.

Dan