Not trying to stir the pot, what OCTANE gas do you run in your saws?

[Freakingstang]

I might be fairly new, but I haven't asked "what ratio to run". I have searched and got quite a kick out of all the ratio posts. I am not even going to mention the ratio I run, as it as worked well for me the last 5-6 years.

My question is, is there any benefit from running a higher octane gas vs a lower octane? I normally run 87 in the winter and 89 during the summer. Based on my car background, higher octane is better with more compression and engine mods, but 87 is easier to ignite in cooler weather. I just performed a muffler mod on one of my 365's and wondered if I should switch to higher octane or not.

Thoughts, suggestions? Not trying to open a can of worms, just trying to become more knowledgable.

Thanks
Steve

 

[Tree Sling'r]

91

 

[clyde]

spend the extra pennies and get the highest pump gas you can get 91-93.

 

[Freakingstang]

91 octane? never heard of it in my area. We have 87,89, and 92 or 93 depending on the vendor.

Is there a difference in fuel vendors? Such as, BP uses more alcohol in their fuel to keep it from gelling/freezing. Should I stray away from fuels with more alcohol in it?

 

[clyde]

yes, if you can find fuel that is not th e"re-formulated" stuff, buy it!

 

[pinus]

Here gas octane is determined by the chemical analysis which gives the numbers some about 5-10 units higher than with the test engine method and the common gas for cars is 95 octane here. Available is 91 and 98 also. With chainsaw I using 95 and 98. With 98 saw engine runs clearly better, especially in winter.

 

[Tree Sling'r]

91 octane? never heard of it in my area. We have 87,89, and 92 or 93 depending on the vendor.

Is there a difference in fuel vendors? Such as, BP uses more alcohol in their fuel to keep it from gelling/freezing. Should I stray away from fuels with more alcohol in it?

I don't know about your area, but every western state seems to have different emissions - different octanes - I live in CA and I am surprised that they don't make us run something higher.

 

[bikepilot]

I run premium pump fuel which is rated at 93oct here. Note that the US uses a different octane rating system than most of the world.

I suspect my saw would be fine on regular fuel, but I actually use the left over mix from my race bikes in the saws and other lawn equipment. The bikes need 93+ octane so that's what ends up in the saw.

 

[Freakingstang]

...<snip>... With chainsaw I using 95 and 98. With 98 saw engine runs clearly better, especially in winter.

Now that actually makes sense, I can't believe I didn't think about it sooner. I never run the modified cars in the winter...(tracks closed, and no fun in the snow!). The colder,denser air would run better with a high burn rate than the lower octane would...

Running lower octane like I have been could actually cause a lean condition with predetonation with the colder, denser air and cause some damage....

Looks like I need to get some higher grade fuel and retune the carb...

 

[Lakeside53]

Ben's comming... You said "pre-detonation"

I use Chevron 89 or 91 (one of the few out here that doesn't have alcohol in it in the winter).

 

[ShoerFast]

Frankinstang

Your on the right track, perhaps ahead of the learning curve with your testing so far!

Octane really dosant have much to do with how gas fires from cold start, in fact the cheap stuff might fire better when it's really cold?

Cold firing gas is also a good "vapor locking" gas,,,, it has more to do with it's "RVP" or Reed Vapor Pressure. You could test this your self, cap a small pipe with a 1-30 psi gauge and fill with your gas, stick it in a cup of coffee,(to heat the pipe),,, when it's at 150 deg. the pressure is your RVP,,,,, you're looking for about a +15psi in the winter, and your 8's or 9's are a good summer gas. (depending on your area)

But a good supplier will take care of this,,,, it's not always true, but some of the gas stations that have there own brand of engine oil will also blend good gas.

If you pull spark-plugs a lot, sometimes inauditible per-ignition will show up as a tanish powder coating on the porcelin ( at a very high temp, gas that is not burning like you want it to, has pocket explosions, that can add a color to the plug)

For me, it's only .10 - .15 cents a gallon more, for the good stuff for my little engines! As my service van gets the cheep stuff and is happy with it.

Kevin

 

[Stumper]

I run midgrade in the winter and premium in the summer. Most of the newer saw manuals specify what constitutes mid grade at sea level.Those who spend all of their time at low elevations may not be aware that different octane formulations are sold at highter elevations. Where I live "regular " is 85 , 87 is midgrade and 90 is premium. I run premium in summer because I have found that I have fewer vapor lock/gas boiling in the tank problems when doing so.

 

[Freakingstang]

Frankinstang
< snip > ...

Octane really dosant have much to do with how gas fires from cold start, in fact the cheap stuff might fire better when it's really cold?

Kevin, that is why I always ran the "cheap stuff" in the winter. The lower ignition point of the lower octane helps in cars in the colder temps. It is easier to ignite. Most detonation I've ran into was really high temps in the summer (on the modified engines) Never ran into it in the winter as I never ran them. lol.

For me, it's only .10 - .15 cents a gallon more, for the good stuff for my little engines! As my service van gets the cheep stuff and is happy with it.

Kevin

Sounds good, the service truck I have gets the cheap stuff, although the company supplied gas card might make me get a tank or two of the good stuff (when I need the 2 stroke tank filled) lol.

 

[Fish]

118 1/2!

 

[bwalker]

Couple points here.
There is no such thing as "predetonation". Detonation and pre ignition are two ,sometimes interrelated, but differant events.

Low temperaturte volatility of gasoline is set by the EPA to reduce evaporative emmsions. As a result premium and 87 have the same low temp properties.
Premium doesnt burn, cooler,slower or have less energy than 87.

 

[SWE#Kipp]

husqvarna's Aspen fuel 95 octane 50/1

 

[Lakeside53]

Ben's comming... You said "pre-detonation"

I told you he would!!! (a few posts back)

 

[bwalker]

I hate it when people use that term!!

 

[pinus]

Now that actually makes sense, I can't believe I didn't think about it sooner. I never run the modified cars in the winter...(tracks closed, and no fun in the snow!). The colder,denser air would run better with a high burn rate than the lower octane would...

Running lower octane like I have been could actually cause a lean condition with predetonation with the colder, denser air and cause some damage....

Looks like I need to get some higher grade fuel and retune the carb...

There can be many reasons why 98 compared to 95 works better.
Gas is sold by/from lot of suppliers/sources. Quality of gas varies a lot of here too. For my car, which moves all the time in different places I get gas from different gas stations. For the saw gas I go to the nearest station to my home and get gas from there, all the time from the same place.
So, 95/98 issue gan be related to the this also
Not too much different gas brands to compare.

 

[ShoerFast]

Good pint Ben

Couple points here.
There is no such thing as "predetonation". Detonation and pre ignition are two ,sometimes interrelated, but differant events.

Low temperaturte volatility of gasoline is set by the EPA to reduce evaporative emmsions. As a result premium and 87 have the same low temp properties.
Premium doesnt burn, cooler,slower or have less energy than 87.

Good point Ben

Sometimes we get into a rut calling thing by there common name, it takes from the understanding. Like calling engines moters,,,,,

But the point to plunder , by any name if gas that burns uncontroled,,, if the flame front starts from 2 differant points and rise the pressures to fast can cause a detonation that explodes the rest of the mixture,,,, or things like too advanced ignition timming that pushes a flame front as the piston is still compressing,,,, causing an explosion (or pocket explosions) Can be termed as detonition.

Just for grins , as kids we would take runners, that were heading to the scrapper, and start them, drain the water to see how long they would go,,,just dumb fun,,, but most all of them would start a very pure engine knock, some wouldent shut off if you tried. Would they be called pre-igniters or detenators, as it sounds the same.

But there are just so many vairables to the making of pump gas to think that the EPA tests every batch for it's RVP, just the final step on how it's cooled can determan the amount of propanes and butains that are drawn off, to say that there are no differances. that, "As a result premium and 87 have the same low temp properties." as there are differances from batch to batch, and as they try to remain consistant, were talking real lynda here!

Just let gas set around for awhile and it will loose some of it's RVP,,,,,ever have something just not want to start, and try freash gas and it goes?

Kevin