Fuel octane rating

[Ricardo Oscar Fiegel]

Good morning, does anyone know what octane rating is recommended for fuel to be used in Stihl machines? And also the percentage of ethanol in the composition?

 

[buzz sawyer]

89 is what the book shows for my ms361. I use REC 90, non-ethanol in everything. As long as you don't leave it in the saw for months, 89 with 10% ethanol is fine.

 

[Ricardo Oscar Fiegel]

89 is what the book shows for my ms361. I use REC 90, non-ethanol in everything. As long as you don't leave it in the saw for months, 89 with 10% ethanol is fine.

That's what I thought, here in Brazil the fuel used is 87 octane and 30% ethanol. It's a miracle they work relatively well

 

[epo]

Good morning, does anyone know what octane rating is recommended for fuel to be used in Stihl machines? And also the percentage of ethanol in the composition?

Since you use a research octane number at gas stations in Brazil, the general minimum is 90. Stihl also has versions of chainsaws with reduced compression ratios that can use fuels with even lower octane ratings.

Good luck with 27% ethanol in your fuel.

 

[sean donato]

Octane isn't rated the same throughout the world. Your owners manual/dealer would be the best to point you in the right direction. Anecdotally, they are low performance engines and don't require high octane fuel, any "regular" grade gas will work. Can't help on the corn juice %. So long as the carb can be adjusted to flow enough fuel it won't be an issue unless it sits for a long period.

 

[Ricardo Oscar Fiegel]

Since you use a research octane number at gas stations in Brazil, the general minimum is 90. Stihl also has versions of chainsaws with reduced compression ratios that can use fuels with even lower octane ratings.

Good luck with 27% ethanol in your fuel.

Regular gasoline- 87 IAD (91 RON)

 

[Mad Professor]

Since you use a research octane number at gas stations in Brazil, the general minimum is 90. Stihl also has versions of chainsaws with reduced compression ratios that can use fuels with even lower octane ratings.

Good luck with 27% ethanol in your fuel.

If you look in the IPLs many saws have two base gaskets of different thickness.

You just enough octane to prevent detonation. Better on the safe side a couple numbers higher octane.

 

[bwalker]

Since you use a research octane number at gas stations in Brazil, the general minimum is 90. Stihl also has versions of chainsaws with reduced compression ratios that can use fuels with even lower octane ratings.

Good luck with 27% ethanol in your fuel.

The concerning part about that whole deal is the absolutely piss poor blend stocks that that are used to hit 90 RON with 30% ethanol.

 

[ballisticdoughnut]

I prefer (R+M)/2 rating since it’s more of a real world number. 30% ethanol is insane to me. Straight ethanol is 35% oxygen by weight. In the US that would equate to 3.5% oxygen content by weight at 10% ethanol (E10) which is standard pump fuel here. At least where I live.

 

[bwalker]

I prefer (R+M)/2 rating since it’s more of a real world number. 30% ethanol is insane to me. Straight ethanol is 35% oxygen by weight. In the US that would equate to 3.5% oxygen content by weight at 10% ethanol (E10) which is standard pump fuel here. At least where I live.

You are absolutely right R+M/ 2 is more realistic than RON. MON is more indicative of how small engines are ran. So using it as half the octane rating is a step in the right direction.

Once you adjust your carb tuning accordingly the increased O2 makes more HP. This is provided you have enough adjustment to compensate.
The problem with 30% is the issues with ethanol become worse when you increase the amount 3x. To make things even worse ethanol is a high octane stream. When the level is 30% it allows absolute garbage to be blended in and still hit 90 Ron.