Octane question.....

[sloch24]

I have some older saws that call for 87 octane, and a ms440 that calls for 89 octane.. what do I do if I want to run one mix? I'm running 80:1 Amsoil... I've always run 87 without a problem in my 031 and 012, but the MS440 is new territory for me, and I don't want to cause it any harm. The 031 manual specifically states not to run high octane fuel "Never use high octane fuel as it contains benzol which will permanently damage the carburetor diaphragm."

Thanks!

 

[OilHead]

First off I'd stop mixin at that ratio & get back to 50 or 45 to 1 . Then use nothing but the best pump gas you can find . :deadhorse:

 

[Nitroman]

Benzol is the German common name for benzene. All gasolines in the US contain benzene.

 

[oneoldbanjo]

Buy 89 or 93 pump gas from the pumps at your local gas station and it will work fine. If you are not going to be using the saw for a few months empty the tank and start the saw and let it idle until it stops. The new pump gas does not keep well and can go bad really fast.

I would recommend you follow Stihls recommendations and mix your fuel and oil at 50:1. I would certainly not mix at 80:1 for your saws. I have a Sherco Trials bike that I mix at 80:1 like the manual says to do - but it is not run at full throttle for anything but short bursts and the saw is run at full throttle a lot. The trials bike engine runs slow most of the time and the muffler will clog up if you run a fuel mix with more oil in it - the saw will be running over 12,000 rpm while cutting and needs a good oil supply.

I have two cans of fuel mixed - one at 80:1 for the Sherco and the other one at 50:1 for everything else. I have older equipment that is supposed to be mixed at 40:1 and some vintage motorcycles that are supposed to be mixed at 20:1 - but those were all built before modern 2 stroke oil was made and they all run fine at 50:1 with sythetic oil.

 

[sloch24]

You really think that you need to run synthetic oil at 50:1? I've been running 100:1 for the last few years in all of my small engines (That's what the bottle says (unless you run your equipment commercially)). I read somewhere in one of the posts that someone is running 80:1, so I thought I'd give that a try... but 50:1? Why am I running synthetic at all? Is it better just to run conventional oil? (Stihl Oil)?

The reason that I started running the Amsoil is because I have about 10 different engines that call for different mixes. I thought it was convenient, and until now I have heard nothing bad about running the leaner mix.

Thanks

Oh, I almost forgot.. I also always mix my fuel with sta-bil because I don't usually go through a can of fuel within a couple of months..

 

[oneoldbanjo]

I personally am not willing to gamble my $ 700 - $ 1,000 saw with an 80:1 mix. I do not know what Amsoil would do if your saw siezed at mix rates up to their claimed 100:1 ratio - but I am sure the warranty coverage from Stihl would not be real certain if you were using mixes that had that little oil in them when they recommend 50:1 in the manual.

I am using Mobil 1 2T at 50:1 in my saws and vintage equipment, and 80:1 in my water cooled motorcyle.......just like the manufacturers instructs me to do.

Let me know how your experiment turns out......

 

[sloch24]

Okay Okay Okay!!!

I just added enough amsoil to my mix to make it 50:1... Sounds like after this oil is gone I'll go to the Stihl Oil...

Definitely high octane fuel though, right? Even though my older machines called for low?

Any thoughts on sta-bil?

Thanks for the opinions so far...

 

[walexa07]

Run stihl ultra and it contains fuel stabilizer in it........no need to stabil with that oil.

Waylan

 

[oneoldbanjo]

Stihl recommends a "mid-grade" gasoline with a minimum 89 octane rating. Premium 93 octane won't hurt a thing - but is probably not necessary. Use 89 and I am sure all your saws will not have any problems caused by fuel problems. I only add Sta-Bil when I get to the winter season as the fuel will sit a bit longer - this time of year I use it up quickly in the motorcycles and trimmer.

In one of your earlier posts you questioned as to why you should run sythetic at 50:1. My response is that my Sithl 029 was 12 years old when I sold it and it still ran great and I never had a fuel, smoke, carbon or oil problem. I want the same great service from my newer saws. I have always used good oil and mixed at the recommended ratios and I have never had to take an engine apart to fix any internal mechanical problems. I am old enough to remember when we mixed oil for the saws and motorcycles by dumping a quart of oil into a five gallon can and then we filled the can up with gas and shook it for a bit. Our saws and motorcycles smoked and always had a bit of oil residue in the exhaust. Modern synthetic at 50:1 burns much cleaner and protects against wear much better - so I use it in all my 2 cycle engines at the recommended mix ratios. When it comes to very lean ratios and new even better methods......I will accept it when the equipment manufacturers who provide warranty coverage are willing to accept it.

 

[lectrocrew]

Octane thread?

Premium 93 octane won't hurt a thing - but is probably not necessary.

I would like to hook an exhaust gas anylizer to my saws and try different octane fuels to see at what point higher octane fuel ceases to contribute to complete power stroke combustion and begins waiste power potential in the form of incompletely burned fuel out the exhast pipe.
The following pictures are of my MS660 muffler after ~45 minutes of run time using 110 octane leaded gas mixed with Stihl HP Ultra full synthetic oil.

I do have my carb adjusted slightly rich at WOT since it is a brand new saw but regardless it looks to me like theres a good amount of combustion trying to take place in the muffler due to the fuel not burning completely in the combustion chamber, but I'm open to any thoughts, analysys, theories ect.

Click on #s below for pictures:
I have a DP front cover ordered with a spark arrestor screen in the area where the present solid cover looks to have sustained quite a bit of heat. I'm currently fabricating a whole new baffle in place of the stock one I modified on the front as seen in the picture just for this reason.
Note: The oil spot on the cover happened after dissassembly.


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[Wicked500R]

I just added enough amsoil to my mix to make it 50:1... Sounds like after this oil is gone I'll go to the Stihl Oil...

Definitely high octane fuel though, right? Even though my older machines called for low?

Any thoughts on sta-bil?

Thanks for the opinions so far...

Bwahhhhh... I'm the Guy that runs Amsoil Sabre 100:1 mixed at 80:1. That stuff is the ####e!! I'll never use anything else in any of my 2 strokes!! Whada' difference. I HIGHLY recommend it! Amsoil makes the BEST oil in the industry so I trust them!
http://www.amsoil.com/storefront/atp.aspx

I'm NOT plugging NON sponsors

 

[sloch24]

Makes sense to me... I'll be running 50:1 and 89 octane in everything... My saws are the most expensive two strokes I own.. I'd rather mix according to them.

Thanks for the info on the ultra.. It probably won't cost me any more to buy the stihl oil when you figure that I'm paying for sta-bil as well.

 

[milkie62]

husky now says 89 octane

I was at the Booneville Woodsmen days.Husky rep said they are now recommending 89 octane over the higher octane only because since fuel is so expensive that not as many people are spending the extra on 91 0r 93 octane so it sits longer in the tank at the pump and develops more moisture in it over the other two grades.Right now i am running cam 2 at $6/gal and 40:1 oil mixture.Plugs are nice and tanAt least the cam 2 does not have ethanol in it.

 

[slabmaster]

I was at the Booneville Woodsmen days.Husky rep said they are now recommending 89 octane over the higher octane only because since fuel is so expensive that not as many people are spending the extra on 91 0r 93 octane so it sits longer in the tank at the pump and develops more moisture in it over the other two grades.Right now i am running cam 2 at $6/gal and 40:1 oil mixture.Plugs are nice and tanAt least the cam 2 does not have ethanol in it.

Who sells cam 2 in you state?Does it have lead in it?

 

[oneoldbanjo]

I would absolutely love to see some dyno numbers and actual testing of an engine with a carb and a simple magneto that is designed to operate on 87 fuel - with the use of 87, 89, 93 and 110 octane fuels (Engines with fuel injection and engine management don't count - as they will make adjustments for the different fuels). It may even require several different tests as a low compression 2 cycle engine may be affected differently than a 4 cycle engine.

It would be very interesting to see what affect the fuel has on the engine performance and temperatures. I hear lots of rumors about high test gasoline burning slower and hotter.....and I don't believe the testing would support that claim. High test gasoline is more resistant to detonation - but does not necessarily burn slower than a gasoline with a lower octane rating. I have never seen any actual testing to support the claims that a moderatly higher octane reduces power - however when you jump to exotic racing fuels I don't doubt that the low compression engine may not perform as well without changing mixtures, timing, etc.

 

[walexa07]

I believe for a dyno to be relevant, same saw with different fuels would have to be tuned to the same out of wood rpm before put on the dyno. 100LL runs rich when the saw is jetted for pump gas and must be leaned to achieve the same rpm out of wood. Just my thoughts.

Waylan

 

[Philbert]

Octane

I believe that most of the chainsaw manuals specify a MINIMUM octane.

All of the chainsaw reps and dealers that I have asked on this topic have recommended using higher octane fuels to reduce fuel problems. At 40 cents a gallon more, it's a lot, but since you only use so little compared to your car or truck, it only adds up to 40 cents.

That and all the standard stuff. Use fresh gas. Drain the tank and run it dry. etc.

Philbert

 

[stevethekiwi]

octane rating is resistance to self ignition. higher octane, more resistance.

unless you're raising your compression, a higher octane wont do stuff all except cost ya. higer octane fuels at the pump are for cars with higher compression so they dont self ignite, you wont notice a power difference by putting 98 octane into a motor designed for 91.

stk

 

[oneoldbanjo]

On a dyno run I would like to see the affect of not making any tuning changes. Take a saw that is set up for 89 and run it with 93, 110, etc. without adjustments. Then later the the saw could be run with adjustments to see if the increased octane made a difference in the fuel settings. One of the problems I see with making adjustments is the change caused by the adjustments themselves causing different readings. I believe a large number of "normal" consumers do not make adjustments (Members of this site can not be classified as "normal".

 

[walexa07]

On a dyno run I would like to see the affect of not making any tuning changes. Take a saw that is set up for 89 and run it with 93, 110, etc. without adjustments. Then later the the saw could be run with adjustments to see if the increased octane made a difference in the fuel settings. One of the problems I see with making adjustments is the change caused by the adjustments themselves causing different readings. I believe a large number of "normal" consumers do not make adjustments (Members of this site can not be classified as "normal".

I agree with you..........run the dyno both ways. The thing that has me wondering is if the saw is tuned for 89 to run 14k rpm out of the cut........then you put in 100LL which will then run rich, so you lean it out to 14k out of the cut, you are essentially getting the same rpm with less fuel. So something has to give. If you get the same power with both, that means the btu content of the 100LL must be higher since you have the same power with less fuel. I'm not the best at putting my thoughts on paper, but maybe this makes sense?

Waylan