1970's Stihl fuel recommendation.....no high octane. What should I use today??

[MikeRock]

In the '70's and early '80's, my Stihl manuals all said not to use high octane. So regular, leaded was the choice. Now with ethanol eating everything it touches, what is the recommendation for fuel for these vintage saws? I have Stihl 031's, 041's and 075's.
Thanks.

 

[Brufab]

I run 89-93 octane ethanol free gas in my 1960s 59-88cc saws with echo red armor oil. Works great.

 

[MMG]

I think in the early 70s they could but 100+ at the pump. Stay with alcohol free pump gas and your favorite mix oil and you should be fine.

 

[cookies]

In the '70's and early '80's, my Stihl manuals all said not to use high octane. So regular, leaded was the choice. Now with ethanol eating everything it touches, what is the recommendation for fuel for these vintage saws? I have Stihl 031's, 041's and 075's.
Thanks.

back then fuel was often higher octane than we see at the pump now, often it was 89 that was sold as regular and 100 or even higher as no knock aka premium. This requires carbs to be adjusted to accommodate the different octane fuel. Higher octane requires more fuel ( higher octane burns at a shorter duration requiring more fuel for the same length of burn). Adjusted for regular but fed premium fuel with a 10+ point difference can result inaudible preignition from running lean + overheating and over revving.
Any fuel not containing ethanol is a better choice for equipment esp things with metal tanks and carbs..the damn ethanol eats them or the water it draws into the ethanol when allowed to sit in the bowl then fuel/ethanol evaps off leaving jelly/rust and that wreaks havoc in the carb body if you unknowingly try to start it .
I get 93, 91, or 89 non ethanol around here depending where im stuck buying more. If i change from 93 to 89 or vise versa the saws carb require a tiny adjustment on the H side. Changing from 93 to 89 I have to turn it in 1/16 ish of a turn or it bogs and 4 strokes when cutting. For my one 1960's saw I just add one cap full of 2 cycle oil to its tank then fill with my regular 40-1 mix.

 

[sb47]

I always try to use ethanol free fuel but the only place I can get it is a long drive so I tend to just use 10% ethanol pump gas. As long as you run your equipment dry and don't leave any fuel in your saw I have had no issues. The trick is to never leave a saw with fuel in the system. Ether run it completely dry or dump the left over fuel out and run it till it uses all the fuel in the system.

 

[Squareground3691]

I run 95 octane ethanol free in all my old and new saws from 70’s to present day no issues with old saws at all

 

[Squareground3691]

I run 95 octane ethanol free in all my old and new saws from 70’s to present day no issues with old saws at all

 

[ChillyB]

Around here one can still find 87 real gas but no high octane. As such I'm thinking not a good idea to mess with base gasket elimination and pop-up pistons.

 

[ericm979]

There are two octane rating systems used in the US: the motor method and the research method. One produces higher numbers for the same fuel than the other. Now days everyone uses an average of the two. I.e. what's rated 87 on the pump might be 82 MON and 92 RON (this is straight from a US petroleum standards doc).

But in the early '70s I'm pretty sure I remember pumps with just the RON number. I can't find a reference that says when R+M/2 was mandated but I think it was the mid to late '70s.

I'd run the highest octane pump fuel you can find, ethanol or not. And check the plug for signs of detonation. But chain saws are industrial engines not race engines so unless modified they will probably run fine on pump premium.

 

[Backstage]

I’ve been told an engine needs more compression than chainsaws usually have to really get the benefit from higher octane. Perhaps the manual was more saying more of a “save your money”.

The premium gas blends may be generally better quality though, so there's that? Speculation. Either way, E0 fuel definitely hydrate slower at a minimum, and chainsaws run like crap on water. In my area E0 rec fuel is basically 90, so that’s what we use.

 

[ChillyB]

High octane fuel is less energetic and burns more slowly, and therefore has a wider margin to detonation. There is no advantage to it UNLESS running an engine with higher CR. Or when a "standard" CR engine is heavily loaded and running hot and hard (pulling heavy trailer, headwind, 110 degrees, uphill...).

Running the wrong oil mix also affects the fuel's octane. Oil lowers octane, I think? So running 40:1 in a saw that expects 50:1 might not be a good idea.

 

[sb47]

I understand what high octane is and it's uses. I also understand most if not all stock chainsaws are fairly low compression. However when I was racing motocross I always had plenty of race gas on hand and tried it in my saws. The race gas I used in my bikes was VP U4.4 and is an oxygenated 105 octane fuel and is a direct poor in replacement for any 2 or 4 stroke engine. I did notice a slight difference in performance. I found I could bear down harder on long cuts without stalling the chain vs regular 87 pump gas. However it was not worth the high cost of running race fuel for the slight increase in performance.
Unless you are running a race saw and after every once of performance you can get, it's not worth using.

 

[Squareground3691]

Husqvarna’s premix canned fuel is all 95 Octane, Stihl ‘s is 93

 

[anlrolfe]

I've found a local gas station that sells e-free Recreational 90 octane.
I've come to use this for my outdoor power equipment along with a quality oil.
Remember - old gas is bad gas, especially if it's got ethanol in it.

Try this link for e-free in your area
Pure-gas dot org

 

[torch]

In the 1970's the predominate method of raising the octane rating of gasoline was to add lead (TEL). Environmental concerns and the health risk aside, lead was also a leading cause of spark plug fouling. Since there are no valves to protect in a 2-stroke engine, maybe Stihl felt the extra lead was detrimental?

 

[lohan808]

Like the other fellas here, I would recommend ethanol free gasoline. I use saber oil for my ope except when I need to take it for service under warranty. Then a careful amount of manufacturers' oil type to keep the guys at the shop cool headed.

 

[lohan808]

Like the other fellas here, I would recommend ethanol free gasoline. I use saber oil for my *** except when I need to take it for service under warranty. Then a careful amount of manufacturers' oil type to keep the guys at the shop cool headed.

You guys really need to get a handle on your censorship program as my *** was O.P.E.

 

[torch]

I use saber oil for my *** except when I need to take it for service under warranty. Then a careful amount of manufacturers' oil type to keep the guys at the shop cool headed.

Nothing wrong with Saber. Both Stihl Super and Saber Pro are rated JASO-FD and ISO-L-EGD. You are in the US, so Magnuson-Moss act applies to you.