What octane is best, and why

[pbillyi69]

i have ran the 100ll before an not noticed any problems but my stihl br600 was not nearly as snappy and i adjusted it to be as snappy as it could. its weird i know. i just mixed the two and fixed the oil readjusted it and it runs like it should.

 

[davidwyby]

Does evaporation increase or decrease octane?

 

[Duane(Pa)]

Does evaporation increase or decrease octane?

Probably decrease. Otherwise racers would be boiling their fuel to make it better...

 

[pbillyi69]

or has no affect at all.....i dont know but it doesnt seem like it would change it in non ethanol gas

 

[davidwyby]

It decreases it.

Month old 87 octane gas made my 395 surge after long cuts. VP bottled premix fixed that and made it run better.

 

[huskihl]

It decreases it.

Month old 87 octane gas made my 395 surge after long cuts. VP bottled premix fixed that and made it run better.

And that’s the reason I believe the manufacturers recommend 91+ octane. If a fuel loses octane or volatility it will cause the saw to heat up and run lean.

 

[davidwyby]

I need to try the 2166 with the VP and see if that's why it was being a booger too. I bet it needs carb kit....maybe even why the 3120 was acting up?


...and the 2139...

 

[huskihl]

I need to try the 2166 with the VP and see if that's why it was being a booger too. I bet it needs carb kit....maybe even why the 3120 was acting up?

Could definitely be the cause

 

[rogue60]

I've had detonation in a stock ms660 before running stale fuel it was low octane to start with. I put the pics up years ago of the damage didn’t seem to effect the saw long term got many years out of it.
Looks like melted air bubbles on top of the piston and squish band I knew something was up by how hot the saw was running still got what I needed done eventually got fresh fuel problem solved.

 

[pbillyi69]

huh interesting. i made some gas with equal amounts of 100ll and 92 clear gas which makes 96 octane of slightly leaded saw gas at 40:1 and everything i put it in runs well and it lasts quite a while

 

[davidwyby]

I know 110 don't run for doodly!

 

[Stump Shot]

87 E-free w/40to1 chainsaw oil with fuel stabilizers in it. have let some of the antique fleet sit for a year or more and start 'em right up and run 'em without fuel system repairs beforehand. Makes good power too with a strong exhaust note.

 

[mrxlh]

Ask the Karens....

Meh, too many variables….

 

[davidwyby]

87 E-free w/40to1 chainsaw oil with fuel stabilizers in it. have let some of the antique fleet sit for a year or more and start 'em right up and run 'em without fuel system repairs beforehand. Makes good power too with a strong exhaust note.

It’s still in the 90s here and gas Evaps like crazy going thru temp and elevation changes in the back of my truck.

here’s the vid :

 

[pbillyi69]

you could try a metal can to help with evaporation

 

[FederalQ]

87 E-free w/40to1 chainsaw oil with fuel stabilizers in it. have let some of the antique fleet sit for a year or more and start 'em right up and run 'em without fuel system repairs beforehand. Makes good power too with a strong exhaust note.

The only E-free around here is 91 octane and at times well over $1 per gallon more than 87 octane.

 

[davidwyby]

I'm gonna try the little round metal cans the premix comes in and keep them full and tight. No air for evaporation. The plastic can has a lot of surface area for the gas to evap.

 

[pbillyi69]

i figured out a couple of yeas ago that the gas stayed fresh way longer in metal cans when my grand father passed and i took his metal gas can that had really old gas in it and it only barely started to smell different and it was really old it burned just fine in my mower

 

[davidwyby]

I'm gonna try the little round metal cans the premix comes in and keep them full and tight. No air for evaporation. The plastic can has a lot of surface area for the gas to evap.

It didn’t work. Cans bulged in the sun…dunno if they would actually pop or not…

 

[Funky sawman]

The only E-free around here is 91 octane and at times well over $1 per gallon more than 87 octane.

Yea e-free premium 91 octane gas here is 4.51 a gallon. Getting old paying that much cause up till today I been burning about 1.2 gallons a day 5days a week. Then you add the red armor mix and now we are up to over 7 dollars a gallon! I only use premium 91. I've actually seen a slight tuning problem when trying to use 100 av gas low lead in stock compression saws.