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87 octane in ms270?

MooneyPilot

MooneyPilot

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Whatever works for you, man. Personally, I think ultra sucks as oil, and it smells unbelievably awful in the exhaust, so I'd never run it. Have I run ethanol gas more than a month old? Yes, but would I recommend it to someone? No.

I really don’t care what it smells like and I have never smelled anything bad with HPUltra regardless of the gas I mix it with. My personal experience since my Stihl dealer told me to use HPUltra and 93 octane out of the E10 pump has been complete flawlessness with everything I’ve run it in. The gas has varied, but the oil has been HP Ultra ever since he told me that which was at least 6 years ago. I’ve mixed it mostly with 91 or 93 octane out of the car gas pump, but recently started using AVGas. I have had several cans at different locations and have used mix that I know for a fact was stored at least a year with no problem of any kind.

People should use what fuel and oil they think is best. Although I like to use higher than 89 octane, every gasoline type that I’ve mixed with HPUltra has been stellar! As long as that success continues, I will stay with it. There may very well be a combination out there that is better, but until this one no longer works well I will stick with it. I learned a long time ago that once something is running well, don’t screw with it until it no longer runs well. For those of you using something different that is working well for you, I think you also should stick with your winning combination.

My $0.02,
 
outdoortype

outdoortype

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I don't understand why Stihl and Echo recommend 89 octane. For one thing, chainsaws are low compression compared to other engines. I respect Madsens but many folks are using 87 on here. Not because they're cheap, because they cant find non ethanol with higher octane ratings. I bought gas for my vehicle that was labeled up to 10% Ethanol. My local garage tested the gas and it was E17. My vehicle can handle this but not my saws. I ran 93 octane E10 for years without issue. I have recently switched to 87 non-ethanol only because I haven't been able to find any higher rated non ethanol. I've ran almost 2-1/2 gallons this year in 4 different saws without issue.
 
MooneyPilot

MooneyPilot

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Although the calculated static compression ratio for sure has an effect on cylinder pressure, other factors come into play when determining dynamic cylinder pressure. It is cylinder pressure that determines octane requirement. More specifically cylinder pressure at the time of ignition is what determines octane requirement.The dynamics of a two cycle engine are different from a four cycle.

That said, without extensive lab study I can not confirm or deny that there is any need for increased octane, but I did put a lot of stock in what my Stihl guy told me. How much gas does a chainsaw or string trimmer use anyway? Another fifty cents more per gallon is worth it to me even if the chance of needing It might be extremely remote.

For me another fifty cents a gallon is not going to send me to the poor house, but this is a decision that everyone is free to make for themselves and I’m happy for them whatever they decide. I only speak of my own opinions, and others are very free to have their own.
 
deye223

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Hey guys
I always use 100% gasoline in my equipment and 93 octane.
The only station in my town that had 100% 93 octane fuel no longer sales it.
The only thing I can find in 100% octane is 87. What are the chances I have a problem running 87 100% gasoline.
I use the Stihl UltraHP Synthetic oil.
I guess I should go ahead and say I already bought the 87 fuel and mixed it.
I never knew Stihl required 89 until now. As I always used 93.

My saw is Stock. There are no modifications of any kind done to it.

Thanks for your advice.
How do you know its 100% gas .
And yep I did not read all the thread .
 

sb47

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I didn't need to read the whole thread but the number on the pump that says the octane number. 87 is 87 octane 89 is 89 octane and 93 is 93 octane. Weather it has ethanol in it or not. Octane numbers has to do with the flash point at witch it will combust under pressure. The higher the number the more pressure it takes to ignite under pressure. 87 octane is actually more dangerous then 100 because it takes less pressure for it to combust.


 
PV Hiker

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Just a example snapshot from a Stihl manual below. I take it as a recommendation from Stihl engineers to help in worry free service of their product. Your adjustment will vary from there. Nice thing about computer controlled saws, will adjust for you for various fuel grades and other variables. Sometimes you just need to burn what you have.
  • Says 89 Octane is recommended as a minimum and can use ethanol up to 10%. By the way MotoMix is 93 octane.
  • Watch seasonal grades sold and adjust carb for fuel used. If keep changing fuel grades your saw will run different requiring adjustments. Keep consistent.
  • Ethanol long term storage in carb try to avoid especially in humid climates that attracts moisture.
  • Your elevation, temperature, humidity and chainsaw compression you might run 87 octane and get away ok, but like said above a mere per gallon difference to get 89 is small price to pay.
  • fuel1.JPG fuel2.JPG
 
MooneyPilot

MooneyPilot

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Just a example snapshot from a Stihl manual below. I take it as a recommendation from Stihl engineers to help in worry free service of their product. Your adjustment will vary from there. Nice thing about computer controlled saws, will adjust for you for various fuel grades and other variables. Sometimes you just need to burn what you have.
  • Says 89 Octane is recommended as a minimum and can use ethanol up to 10%. By the way MotoMix is 93 octane.
  • Watch seasonal grades sold and adjust carb for fuel used. If keep changing fuel grades your saw will run different requiring adjustments. Keep consistent.
  • Ethanol long term storage in carb try to avoid especially in humid climates that attracts moisture.
  • Your elevation, temperature, humidity and chainsaw compression you might run 87 octane and get away ok, but like said above a mere per gallon difference to get 89 is small price to pay.
  • View attachment 869583 View attachment 869584
Wait a minute! Consulting the manual is no fun! Whoever heard of doing such a thing? Arguing about opinions and old wives tales is much more fun.:D

Seriously though, thanks Hiker!
 
MooneyPilot

MooneyPilot

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I didn't need to read the whole thread but the number on the pump that says the octane number. 87 is 87 octane 89 is 89 octane and 93 is 93 octane. Weather it has ethanol in it or not. Octane numbers has to do with the flash point at witch it will combust under pressure. The higher the number the more pressure it takes to ignite under pressure. 87 octane is actually more dangerous then 100 because it takes less pressure for it to combust.


This is somewhat useful information regarding octane and road vehicles, but is only part of the story when fueling a 2 cycle off road engines.

When it comes to chainsaws and other 2 cycle engines without oil injection, the fuel equation gets several additional factors beyond octane.
 

sb47

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Just a example snapshot from a Stihl manual below. I take it as a recommendation from Stihl engineers to help in worry free service of their product. Your adjustment will vary from there. Nice thing about computer controlled saws, will adjust for you for various fuel grades and other variables. Sometimes you just need to burn what you have.
  • Says 89 Octane is recommended as a minimum and can use ethanol up to 10%. By the way MotoMix is 93 octane.
  • Watch seasonal grades sold and adjust carb for fuel used. If keep changing fuel grades your saw will run different requiring adjustments. Keep consistent.
  • Ethanol long term storage in carb try to avoid especially in humid climates that attracts moisture.
  • Your elevation, temperature, humidity and chainsaw compression you might run 87 octane and get away ok, but like said above a mere per gallon difference to get 89 is small price to pay.
  • View attachment 869583 View attachment 869584

This is somewhat useful information regarding octane and road vehicles, but is only part of the story when fueling a 2 cycle off road engines.

When it comes to chainsaws and other 2 cycle engines without oil injection, the fuel equation gets several additional factors beyond octane.
RON (Research Octane Number) is normally higher than MON (Motor Octane Number). MON is time consuming and needed standard test engines. MON would be suit your purpose - to determine effect of different ON (engine knocking characteristic) rating.

Two octane numbers are routinely used to simulate engine performance: the RON simulates gasoline performance under low severity (at 600 rpm and 120°F (49°C) air temperature), whereas the motor octane number (MON) reflects more severe conditions (at 900 rpm and 300°F (149°C) air temperature).
 

sb47

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They are two different blends for different purposes and neither number simulates anything. They are scientifically defined.
Ron is (Research Octane Number) MON is the (Motor Octane Number) A pump will show the MON witch is the lower number.
 
CausticUC

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An octane thread is much more dangerous than an oil thread!!
It seems so, and I am definitely the idiot for allowing myself to keep being drawn in and providing information with backup.

"Attention Walmart shoppers there is a sale on high quality virgin toilet paper in aisle Seven, 10 rolls of 60 at double the half price of 30 rolls!"
 
TnShooter

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TnShooter, I guess since Stihl and Husqvarna make 3 grades of saws Homeowners,Farm and Ranch and the Pro saws it might be best to match them up with the 3 octane grades of gas. I thought I did read somewhere that Stihl recommended a min. of 89 octane. In Germany Stihl and Dolmar were designed to run on 100% gas without ethanol. Man I really would hate to drop $1300 or $1400 on a new MS 500i and end of smoking that baby. Shooter after all this conflict I need a week in Gatlinburg.
You don’t want to be anywhere near Gatlinburg this time of year.
Unless you like sitting in traffc?

I don’t want to smoke anything, that’s why I started this post.
Although it’s taken an odd turn. But that’s ok!
How do you know its 100% gas .
And yep I did not read all the thread .
See post #6
An octane thread is much more dangerous than an oil thread!!
I don’t think I’ll be the one to start that....lol
 
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