Stihl Fuel Recommendation?

[bwalker]

I once worked in a plant of one of the big three automakers. They had a mysterious warranty issue of spark plug fouling. They eventually found out that the fuel supplier had run out of regular and substituted premium without telling the auto company since everybody knew that premium was better. The premium gasoline caused the fouling. I use 89 octane in my chainsaw and trimmers, presumably with ethanol, and never have a problem. BUT, I plan my work to run the tank dry within a few days of filling it and do enough work that the purchased fuel in the containers is always used within a month. When the equipment is stored for the season, it is dry.

I'm not buying that at all. I am not saying you are a liar, but rather premium fuel was scapegoated.

 

[bwalker]

I have two choices here so I run the 98.

Premium 98 octane
Benzene 71-43-2 0.1 to 1.0 %
Gasoline, natural 8006-61-9 90 to 100 %
Plus:
Friction Reducer
Cleaning Agent
Rust Inhibitor

91 octane
Gasoline, natural 8006-61-9 80 to 100 %
Toluene 108-88-3 0 to 20 %
Cumene 98-82-8 0 to 20 %
Benzene 71-43-2 <1 %

It's neat that aussie fuel has cumene in it. It's also apparent your fuel is much different than US fuel.

Opening the instruction book which came with my Stihl saw, I note that REGULAR grade fuel is recommended, with a WARNING against using Premium fuel. I have been of the belief and practice (for the past 49 years ) that the higher the octane, the better: High octane enables the saw to run cooler, as well as minimizing problems associated with lo-octane fuel.
To suggest I'm confused might be an understatement!
Any comments or suggestions?
geoView attachment 1180327

Benzol aka benzene hasn't been present in more than trace amounts in US fuel for a long time. Refineries have BRU units to remove Benzene and other aromatics because the EPA dictates it.

 

[bwalker]

I am also going to say that premium and regular are just different blends of the same crap. No magic additives etc. Just slightly more alkylate is blended into premium.
I buy premium because it's ethanol free, but is totally unnecessary in a chain saw.

 

[user 196652]

It's neat that aussie fuel has cumene in it. It's also apparent your fuel is much different than US fuel.

Benzol aka benzene hasn't been present in more than trace amounts in US fuel for a long time. Refineries have BRU units to remove Benzene and other aromatics because the EPA dictates it.

Do you think I might be better off using the 91? I was concerned about perhaps the Toluene and Cumene just being there to bulk it out and up the octane a bit.
I'm thinking that the added stuff in the 98 might mess with my oil ratio and also not burn off properly. Don't need anti rust and the 2 stroke oil is doing it's lubrication thing anyway.
Any thoughts?

 

[bwalker]

Do you think I might be better off using the 91? I was concerned about perhaps the Toluene and Cumene just being there to bulk it out and up the octane a bit.
I'm thinking that the added stuff in the 98 might mess with my oil ratio and also not burn off properly. Don't need anti rust and the 2 stroke oil is doing it's lubrication thing anyway.
Any thoughts?

I would run the lower octane stuff as your fuel doesn't contain ethanol.

 

[thompsoncustom]

My ms170 calls for premiumView attachment 1180566

89 Ron is equal to 84 Octane in the US.

 

[Sloughfoot]

I’ve run 87 to 100+ octane fuel in near every kind of small engine two and four stroke equipment. They all ran fine and still run to this day. Run whatever grade of pump fuel you want it’ll be fine. Preferably non ethanol of course.

Yeh, if anything a higher octane may help a saw run better on hot days. Correct the timing. After all, higher octane simply means resistance to preignite at higher temperatures. It doesn't mean mo powah.

Some auto tunes won't run right on anything but regular at normal working temperatures.

 

[Sloughfoot]

Do you think I might be better off using the 91? I was concerned about perhaps the Toluene and Cumene just being there to bulk it out and up the octane a bit.
I'm thinking that the added stuff in the 98 might mess with my oil ratio and also not burn off properly. Don't need anti rust and the 2 stroke oil is doing it's lubrication thing anyway.
Any thoughts?

98 could theoretically be late burning off, especially in cool weather. Regular may ignite too early in hot weather. Run a tank of each. See what happens.

On 90F+ days I splash a little octane boost in each fill up.

 

[ballisticdoughnut]

Yeh, if anything a higher octane may help a saw run better on hot days. Correct the timing. After all, higher octane simply means resistance to preignite at higher temperatures. It doesn't mean mo powah.

Some auto tunes won't run right on anything but regular at normal working temperatures.

True, air cooled engines tend to run on the hotter side generally speaking. On a 90F day running higher octane certainly wouldn’t hurt. I’ve run VP T4 in my husky 545 MkII which is 97 octane (R+M)/2 and about 6% oxygen content. Saw ran great the autotune handled it perfectly. VP T4 spec sheet.

 

[Sloughfoot]

True, air cooled engines tend to run on the hotter side generally speaking. On a 90F day running higher octane certainly wouldn’t hurt. I’ve run VP T4 in my husky 545 MkII which is 97 octane (R+M)/2 and about 6% oxygen content. Saw ran great the autotune handled it perfectly. VP T4 spec sheet.

I'd wager on a hot day that their would be a noticeable difference running a stock ~150 psi saw and the same ported with ~190 psi. The stock saw would probably run "ok" but the higher compression saw would run significantly better with higher octane.

 

[stihltech]

Here we go again. Look in the book.
Real life in the shop- ALL fuel will have water at some point. Keep fuel less than 90 days. Use a good mix oil.
I find just as much water in non ethanol as in ethanol. 75% of saws coming in the shop have water in the fuel.
So the secret is- clean out the can between fill ups, don't store fuel for long periods.

Problem solved.

Can we talk about something else? Please?

 

[bwalker]

98 could theoretically be late burning off, especially in cool weather. Regular may ignite too early in hot weather. Run a tank of each. See what happens.

On 90F+ days I splash a little octane boost in each fill up.

Octane has nothing to do with resistance to ignition.

 

[bwalker]

Here we go again. Look in the book.
Real life in the shop- ALL fuel will have water at some point. Keep fuel less than 90 days. Use a good mix oil.
I find just as much water in non ethanol as in ethanol. 75% of saws coming in the shop have water in the fuel.
So the secret is- clean out the can between fill ups, don't store fuel for long periods.

Problem solved.

Can we talk about something else? Please?

90 days is really stretching it in hot humid climates.

 

[Sloughfoot]

Octane has nothing to do with resistance to ignition.

What is wrong with your brain?

 

[two4spooky]

Am I the only one that finds it strange in the OP's pic of the manual Stihl states "40:1 with Stihl oil" ? I thought the OEM's were recommending 50:1 across the board. New standard(?) or have I been asleep at the wheel.

Opening the instruction book which came with my Stihl saw, I note that REGULAR grade fuel is recommended, with a WARNING against using Premium fuel. I have been of the belief and practice (for the past 49 years ) that the higher the octane, the better: High octane enables the saw to run cooler, as well as minimizing problems associated with lo-octane fuel.
To suggest I'm confused might be an understatement!
Any comments or suggestions?
geoView attachment 1180327

 

[lone wolf]

Am I the only one that finds it strange in the OP's pic of the manual Stihl states "40:1 with Stihl oil" ? I thought the OEM's were recommending 50:1 across the board. New standard(?) or have I been asleep at the wheel.

Older manual?

 

[bwalker]

What is wrong with your brain?

It's just I know what the heck I am talking about and you don't.

 

[Tomos770]

Engineered fuels work well, yes they are expensive, but you only need to avoid one lean engine failure to recover the cost. I use engineered fuel .....

....when I winterize or store my OPE.

 

[Tomos770]

Higher octane fuel stays fresh longer...

....I think that is oposite....

RON 95 stays fresh for longer then RON 100 <----- fractions are more volatile

 

[Seachaser]

Every mechanic I ever talked to said to avoid ethanol like the plague in small engines. That’s what I do.