Philip Wheelock
Finis Origine Pendet
Please note that Stihl recommends 89 octane minimum.
Stihl recommends 89 octane
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Scientifically, you only need an octane rating high enough to avoid pre-detonation. Any octane high enough to not self-ignite under the heat generated by compression will suffice. There is no other benefit; higher octane does not equate to "more power", etc.
Want to really get this thread rolling? Let's talk about oil and ratios!
Want to really get this thread rolling? Let's talk about oil and ratios!
zogger
Tree Freak
Have you looked at marinas? They might have rec 90 with no ethanol.
danimal
ArboristSite Operative
Higher octane burns cleaner and cooler. I run 89 in both chevy trucks.
With all thecrap in gas anymore, 87 octane is not very good for any engine.
And yes low octane causes pre det.
Run 100 ll in my higher compression saws and the power increases is very obvious. If you put hi oct. in a saw n it loses power, proof compression is low. Where the cut off is I cant say.
I aint no scientist, just a billy who cuts lots of farwood n I kno what I kno from experience.
As for 2 strokes not knowing the difference in octane. Ask the big merc sittn on the back of my bassboat. It just luvs 91 to 93.
With all thecrap in gas anymore, 87 octane is not very good for any engine.
And yes low octane causes pre det.
Run 100 ll in my higher compression saws and the power increases is very obvious. If you put hi oct. in a saw n it loses power, proof compression is low. Where the cut off is I cant say.
I aint no scientist, just a billy who cuts lots of farwood n I kno what I kno from experience.
As for 2 strokes not knowing the difference in octane. Ask the big merc sittn on the back of my bassboat. It just luvs 91 to 93.
1) Stihl's recommendation is partly due to performance, " use 89+ octane" and partly due to government regulations "use up to 10% ethanol."
2) Buy 89+ noE if you can. If not go with ethanol + Startron or similar if you can keep it fresh. Leaded AV gas is just not necessary.
2) Buy 89+ noE if you can. If not go with ethanol + Startron or similar if you can keep it fresh. Leaded AV gas is just not necessary.
danimal
ArboristSite Operative
Conventional 2 stroke or klotts,Scientifically, you only need an octane rating high enough to avoid pre-detonation. Any octane high enough to not self-ignite under the heat generated by compression will suffice. There is no other benefit; higher octane does not equate to "more power", etc.
Want to really get this thread rolling? Let's talk about oil and ratios!
32/1.
If they want my can of saw gas, they will have to pry it from my cold dead fingers
AV gas aint needed. Lead is a nice lubricunt for moving parts tho.
And ya dont have to cut apart a junk car battry to get to da plates to put in da gas can.
Oleo-Mac 999
ArboristSite Member
It is precisely because it is more powerful is that it needs to have more octane to prevent self-detonation. Gasoline of jet aircraft use gasoline between 260 and 300 octane. Cause so many octane? to prevent self-detonation because this gas has a huge calorific value if used in a conventional engine, quickly destroy the engine.
Lots of wives tales about hi/low octane in saws. With the RON & MON ways to catagorise octane our 91 is different to 91 in the US. My experience has been better with standard regular e-free 91 unleaded than with higher octane fuels. More power and cooler. That is opposite to what others claim their experiences to be l realise but my judgement is based simply running them. Even modified high compression saws adhere to this as well. Just what experience has tuaght me. I know in modern high performance cars, they cerainly do benefit fom the premium higher octane fuel but saws....l dunno it has not been my experience.
You nailed it. This is how the Stihl Dealer explained the importance of 89+ octane. To me when I purchased my new saw. And running less octane voids warranty. I run 89 ethanol free with Stihl Ultra HP. Also both Sthil HP and Ultra HP have fule stabilizer.No need to add another product to the mix. Most top shelf mixes have stabilizer.
Ozarker 1
ArboristSite Member
Flame Speed, Octane Number, & Horsepower
http://www.whitfieldoil.com/www/docs/171.284/vp-racing-fuel-
http://www.whitfieldoil.com/www/docs/171.284/vp-racing-fuel-
axe2fall
Hound runner
Octane booster is most likely a high percentage of ethanol
danimal
ArboristSite Operative
Very hi alki content. Ethanol is an oxigenator, increases hp,oct. n flame..bad fer saws...mine anway.
And why is that you may ask?
BECAUSE THEY R MY SAWS
Not sure about the new saws but been running 87 in my modded 064 for over 20 years never had a problem. ( ethanol free)
axe2fall
Hound runner
Octane is often thought of as some kind of highly combustible super refined fuel.
I know people that mix it with old stale gas thinking it will revitalize it. I tell them that 100 gals of high test mixed with a gallon of old gas leaves you with 101 gallons of bad fuel.
It is actually harder to ignite a higher octane fuel than a lower octane fuel. High octane fuel is only beneficial to high compression engines. Octane adds to the cost of gasoline because it is an additive that makes fuel less likely to ignite before the spark plug fires. AKA pre ignition . Pinging, detonation, whatever you call it.
Pressure = heat. . . High compression engines can cause the fuel in the cylinder to ignite before the plug fires due to the heat generated by the pressure of the up stroke.
= Hell on a 4 stroke valve train.
Not sure how all of this could affect a stock 2 stroke engine but personally I would rather have 87 octane E-0 than any high octane fuel with ethanol in it in my stock 026 . . . But what if the compression was higher than average? In that case it would depend on what's available. We are lucky enough to have a marina nearby with 89 oct E-0. I use at least 200 gals yearly in all my small engines. Not available everywhere though. If not available Maybe run E-10 with higher octane in a ported or lowered jug saw, but if that saw is to be stored for a few months, throw a tank of $30 a gal. Tru-Fuel through it . . . Can't believe ranting about octane and ethanol again but does anyone remember Dry-Gas ?
Well that's ethanol. Used to help small amounts of water in your fuel mix in and run through the system. Fine for my 400 small block but not what I want anywhere near my boat or saw.
The crap absorbs moisture from the air.
Btw . . Ethanol is the biggest scam ever pushed down the throats of of the American taxpayer. Well, one of the biggest.
I know people that mix it with old stale gas thinking it will revitalize it. I tell them that 100 gals of high test mixed with a gallon of old gas leaves you with 101 gallons of bad fuel.
It is actually harder to ignite a higher octane fuel than a lower octane fuel. High octane fuel is only beneficial to high compression engines. Octane adds to the cost of gasoline because it is an additive that makes fuel less likely to ignite before the spark plug fires. AKA pre ignition . Pinging, detonation, whatever you call it.
Pressure = heat. . . High compression engines can cause the fuel in the cylinder to ignite before the plug fires due to the heat generated by the pressure of the up stroke.
= Hell on a 4 stroke valve train.
Not sure how all of this could affect a stock 2 stroke engine but personally I would rather have 87 octane E-0 than any high octane fuel with ethanol in it in my stock 026 . . . But what if the compression was higher than average? In that case it would depend on what's available. We are lucky enough to have a marina nearby with 89 oct E-0. I use at least 200 gals yearly in all my small engines. Not available everywhere though. If not available Maybe run E-10 with higher octane in a ported or lowered jug saw, but if that saw is to be stored for a few months, throw a tank of $30 a gal. Tru-Fuel through it . . . Can't believe ranting about octane and ethanol again but does anyone remember Dry-Gas ?
Well that's ethanol. Used to help small amounts of water in your fuel mix in and run through the system. Fine for my 400 small block but not what I want anywhere near my boat or saw.
The crap absorbs moisture from the air.
Btw . . Ethanol is the biggest scam ever pushed down the throats of of the American taxpayer. Well, one of the biggest.
there is no'pre-det'
preignition and det are different.
Preignition is a normal flame front started at the wrong time by something other than the spark plug and timing. Usually from a small local hot spot, like a plug thread, bit of carbon, or burr edge of gasket etc. Its not usually an issue unless the engine is under a heavy load enough to heat up these small spots. i.e chain saw is run at hgih rpm and heavy load.
Preignition is controlled by mechanical means, timing or hot spots, not fuel related.
detonation is the sudden and uncontrolled ignition of part of the remaining charge, by heat coming from the normal flame front. As the flame burns across the cylinder, it is heating up and compressing the last part of the charge and that part can self ignite. When the two pressure waves collide, knocking or pinging sound.
Detonation can lead to hot spots to preignition, or preigntion too early can cause detonation. The two can be a viscious circle that destoys and engine in seconds. Racing air cooled two cycle motorcycle engines were quite prone to this.
detonation is controlled by design of combustion chamber (smaller, more centralized, and less squish clearance) or by fuel that reists igniting (higher octane)
Octane is not a fuel additive, it was the reference for the original rating scale. Octane as a fuel was the most detonation resistant at the time, so it was given a basis of 100 as the best. I can't recall, I think cetane was the 0 reference)
Various fuel additives make it detonation resistant to varying degrees, and it is compared by a standard SAE test process with engine design, compression, rpm, load, and temperature to compare various fuels.
A good, high octane fuel resistant to self ignition is desired for spark ignition engines.
A good, LOW octane, or cetane rating fuel is desired for compression ignition (diesel) engines. Basically, squirt fuel in and want it to self ignite quickly.
The ROM and MON methods differ and of course the whole ROM, or MON, or (ROM + MON)/2 ratings confuses people even more.
preignition and det are different.
Preignition is a normal flame front started at the wrong time by something other than the spark plug and timing. Usually from a small local hot spot, like a plug thread, bit of carbon, or burr edge of gasket etc. Its not usually an issue unless the engine is under a heavy load enough to heat up these small spots. i.e chain saw is run at hgih rpm and heavy load.
Preignition is controlled by mechanical means, timing or hot spots, not fuel related.
detonation is the sudden and uncontrolled ignition of part of the remaining charge, by heat coming from the normal flame front. As the flame burns across the cylinder, it is heating up and compressing the last part of the charge and that part can self ignite. When the two pressure waves collide, knocking or pinging sound.
Detonation can lead to hot spots to preignition, or preigntion too early can cause detonation. The two can be a viscious circle that destoys and engine in seconds. Racing air cooled two cycle motorcycle engines were quite prone to this.
detonation is controlled by design of combustion chamber (smaller, more centralized, and less squish clearance) or by fuel that reists igniting (higher octane)
Octane is not a fuel additive, it was the reference for the original rating scale. Octane as a fuel was the most detonation resistant at the time, so it was given a basis of 100 as the best. I can't recall, I think cetane was the 0 reference)
Various fuel additives make it detonation resistant to varying degrees, and it is compared by a standard SAE test process with engine design, compression, rpm, load, and temperature to compare various fuels.
A good, high octane fuel resistant to self ignition is desired for spark ignition engines.
A good, LOW octane, or cetane rating fuel is desired for compression ignition (diesel) engines. Basically, squirt fuel in and want it to self ignite quickly.
The ROM and MON methods differ and of course the whole ROM, or MON, or (ROM + MON)/2 ratings confuses people even more.
Cycledude
ArboristSite Operative
Bought My Husqvarna 61 brandnew in 1981, up until about 2 years ago all I ever used was 87 , when I finally did switch to premium everything seemed the same. Not sure if it's helping anything but I use premium fuel in all my small engines these days because most loggers that I know recommend it.
Rockjock
Addicted to ArboristSite
What the Hell does Stihl know?
Since the introduction of flippy caps, I've lost all respect.
LOL does anyone have a 5 year old to instruct my learned friend on the correct operating procedure of said caps?
