aviation gas v. high octane no ethanol

[ksks]

Is there any benefit to use aviation gas over premium no ethanol in the 2cycle motors?

[ladylake]

 Not unless it's highly modified with really high compression, the lower octane will make more power as it burns faster.   Steve

[Joe Kidd]

Plus there is a small amount of lead(100LL) in the exhaust which can't be good long term. Like the previous post, after about 95 octane there is a slight decrease in power in a non modified saw.

[ksks]

Interesting...

What about difference in shelf life?

[Joe Kidd]

100LL is made to higher purity standards, so I'd say it's shelf life is superior. I don't have access to any, but would like to give it a test run for the heck of it.

[LaegersATC500R]

Why are you considering aviation fuel? What are you up to??

[lone wolf]

This should help.     http://www.madsens1.com/saw_fuelmix.htm

[gologit]

I've been running 100LL av-gas in my saws for several years.  I don't see any real problems with it.  I cut anywhere from sea level to 7000 ft. and if there's any loss of power due to the gas it's not enough to notice.
You might have to retune your carb a little...some guys do and some guys don't.

The thing I like best about av-gas is that it's refined to strict standards and a gallon bought in California will be the same as a gallon bought in Maine.  You can count on av-gas clean and pure.  If you're buying it from the local airport it's filtered and water checked before it ever hits the pump.

Car gas, especially where I live, is always a crap-shoot for quality.  The little mom and pop mini-markets buy gas from brokers and you never really know what's going in the tank. 
With av-gas you know what you're getting.

[Joe Kidd]

Well said Bob.

[mad murdock]

Av-gas will not varnish even if left sitting for more than a year. As an aircraft mechanic by trade, (27yrs +), it is good fuel. There has been a big push for it to be replaced by 2015, but that date has already been changed (pushed back).  It is hard to find a viable substitute, that works as well.  If you are going to use it in extreme cold, it does not atomize as well as lower octane fuels in -10 below or colder.  If you don't plan in using a saw in subzero temps, go fer it. You may experience minor lead fouling on the spark plug, but with regular plug changes, it is not a problem.

[Windy_Acres]

Not unless it's highly modified with really high compression, the lower octane will make more power as it burns faster.   Steve

Just curious, did you read this somewhere, or have you tried it first hand. Ive had exactly the opposite results running 102 octane in 2 strokes. They scream with power, and the power is clean, and you get more and faster rpm's under load.

Ive not tried it in a saw, but 2 stroke "power sports" LOVE the stuff. Next trip to town, Im going to bring some home and give it a try in 3 different brand saws and see if I can tell a difference. The only thing I would expect is harder starting cold.

[Joe Kidd]

I'll just add at least in saws that's the case. If AS was up I could provide some links on dyno tested saws using high octane fuels. Cheers

[acrosteve]

Different that av gas, but I have heard that "race fuel" will not gell in a carb when left sit for long periods.  There is a station around me that sells it, but I have never felt the need.

[Windy_Acres]

I'll just add at least in saws that's the case. If AS was up I could provide some links on dyno tested saws using high octane fuels. Cheers

Ok, interesting, I wonder what is different about a chainsaw 2 stroke, than the rest.... Im still going to give it the test for myself. That or Av gas is the only thing around here, I know I can find that is not blended.

[Joe Kidd]

I'll just add at least in saws that's the case. If AS was up I could provide some links on dyno tested saws using high octane fuels. Cheers

Ok, interesting, I wonder what is different about a chainsaw 2 stroke, than the rest..

Not sure. Let us know your results.

[AdkStihl]

AV gas burns rich and slow, so carburetors need to be tuned accordingly.
Contrary to many persons beliefs, AV gas (or any higher octane fuel) burns cooler and makes less horsepower....it just burns LONGER.
Race engines whether in a car or in a saw have much higher compression. Compression makes horsepower and with it comes heat. More compression - more heat. Higher compression engines need higher octane to prevent pre-ignition -higher octane fuel is resistant to detonation (pre-ignition).
Running pump gas in a high compression engine can be detrimental.
Although I doubt you'll blow any work saw sky high by running 87oct.
I've heard of saws with 220psi + that run on 87oct with no problems.
Running high octane (100oct +) in normal engines doenst really do jack crap except burn cleaner.
If anything....youre decreasing engine output.

A gentlemen I know on another forum recently built a chainsaw dyno. One of the tests was octane.....100oct VS 92oct.
In 2 out 3 different tests, the 92 octane generated more HP than the 100 octane.
The biggest gains were had by advancing the ingnition timing by 6 degrees.

[AdkStihl]

Not unless it's highly modified with really high compression, the lower octane will make more power as it burns faster.   Steve

Just curious, did you read this somewhere, or have you tried it first hand. Ive had exactly the opposite results running 102 octane in 2 strokes. They scream with power, and the power is clean, and you get more and faster rpm's under load.

Ive not tried it in a saw, but 2 stroke "power sports" LOVE the stuff. Next trip to town, Im going to bring some home and give it a try in 3 different brand saws and see if I can tell a difference. The only thing I would expect is harder starting cold.

You should read a little more and perhaps try some in your saw or OPE.
You will notice a few things...cleaner burn, smoother running, lower operating temps, nice aroma.....but higher performance is not one of them.

[LaegersATC500R]

I will give AV a try. There's a small airport not to far from me. I'll pick up 5 gallons. Right now I use 92 octane and use an additive to counteract the effects of ethanol in the fuel. It's hard to say but the saws SEEM to run a bit better during  acceleration.

[ladylake]

 I'm lucky here as I can get 91 octane without ethanol at 2 stations 2 miles away.    Steve

[RCBS]

I finally found a non-ethanol source this summer.  90 octane with no corn.  It's a twenty mile ride and is slightly more expensive, but the peace of mind is worth it.  Especially after seeing hundreds of fuel related issues working in a repair shop for a few years.  This was mostly on generators and pumps.  Not always old gas, but dirt and water as well.  Many people never look in their gas cans/tanks and just assume that since there is fuel present, that it should run. 

I have a coworker who uses AVgas and has good results with it, but he pays more than I do for the non ethanol blend regular gas.

I use corngas in my truck as it is not practical to drive 20 miles to fill up, but I would for sure pay a premium to have pure gas available at all stations.  The truck gets an average of 2mpg better on pure gas.  Why are we not given a choice of fuels?  I'm tired of corn being rammed down our throats.  Read some ingredient labels and you'll see that literally its being crammed down our throats as corn syrup.  Somehow it has become a mainstay ingredient in *everything!

/rant.

[ksks]

Good read.  I do use non ethanol premium in my small engines.

Problem is the gas will sit up to a few months. 

Stilh has its own gas mixture.  Its really expensive, but suppose to last a year.  Just trying to figure how to protect engines that don't get used regularly.  I do add Stabil or Seafoam.  Sounds like that may be the best option father than monkeying with the carb when I don't know what I'm doing.

Thanks for the info.  Very helpful.

ksks

[john_bud]

There is a lot of "marketing" in peoples minds about high octane.  Too much madison avenue and not enough MIT in the mix!


For 2 cycle engines power is lost because there is not enough time to fully evaporate the fuel before ignition AND there is not enough time to complete the burn before the exhaust port is uncovered.   The still liquid portion of the fuel is exhausted partially unburned so there is lost power.  Same as opening the exhaust while still burning the fuel. Lower octane evaporates faster and burns faster, so there is less if those losses.  You dont see this in cars as the rpms for normals highway speeds are much less than a saw's idle.

Just my $0.02

[nmurph]

I have run E10 in all my saws, all of which are modded, some with pretty stout compression, for several years without a problem...much is made of ethanol based on anectdotal evidence. Keep the fuel less than 3 months, use a good quality synthetic oil with a stabilizer, and you won't have a problem. AV gas has a long shelf life, but unless you are running compressions north of 220, the extra detonation resistance is not needed and does lessen performance.

[labdad]

I finally found a non-ethanol source this summer.  90 octane with no corn.  It's a twenty mile ride and is slightly more expensive, but the peace of mind is worth it.  Especially after seeing hundreds of fuel related issues working in a repair shop for a few years.  This was mostly on generators and pumps.  Not always old gas, but dirt and water as well.  Many people never look in their gas cans/tanks and just assume that since there is fuel present, that it should run. 

I have a coworker who uses AVgas and has good results with it, but he pays more than I do for the non ethanol blend regular gas.

I use corngas in my truck as it is not practical to drive 20 miles to fill up, but I would for sure pay a premium to have pure gas available at all stations.  The truck gets an average of 2mpg better on pure gas.  Why are we not given a choice of fuels?  I'm tired of corn being rammed down our throats.  Read some ingredient labels and you'll see that literally its being crammed down our throats as corn syrup.  Somehow it has become a mainstay ingredient in *everything!

/rant.

What he said 8)

[nmurph]

Higher octane does not make a fuel burn slower-

http://www.racegas.com/article/10

[Scottman22]

I make my living with aviation fuels.  Avgas, or 100 Low Lead has an octane rating of 100/130 (100 at leanest combustable mixture/ 130 at richest combustable mixture AT SEA LEVEL). having said that the testing method for obtaining Aviation octane rating and MOGAS octane rating is different.  (I do not know how different).  But I've been told by our Quality Control Specialist that if we tested AVGAS using the same equipment as MOGAS we would get about an average of about 97 octane.

Many of you are right about AVGAS though.  its held to a higher standard during refinery and all throughout the shipping process.  Plus there are absolutely no additives injected during the shipping process.  you can count on consistency no matter where you buy it. plus (as some of you stated) it is typically checked for water and other contaminates daily and it is filtered much better than MOGAS.

The lead content is there for lubrication.  Many of you know that leaded fuel had anti-knocking properties which is why unleaded fuels was such a big deal when it first came out.

I don't have any experience in running it in equipment other than airplanes and cannot recommend using it.  But I will say this.  Keep a lid on the container you put it in because it will evaporate in no time flat!  and be careful handling it.  it has a much lower flash point than other fuels.  it doesn't need much to go boom!

[Scottman22]

......Oh, and if our AVGAS sits still for six months we have to send a sample to the lab. 

[LaegersATC500R]

Don't forget that the oil added to the gas will reduce combustion. Does the oil lower the octane rating?

[beenthere]

I finally found a non-ethanol source this summer.  90 octane with no corn.  It's a twenty mile ride and is slightly more expensive, but the peace of mind is worth it.  ...........................

I use corngas in my truck as it is not practical to drive 20 miles to fill up, but I would for sure pay a premium to have pure gas available at all stations.  The truck gets an average of 2mpg better on pure gas.  ..............

/rant.

I drive almost 20 mile to the non-ethanol station.. as I also get 2 mpg better gas mileage. That is 10% more (18 mpg vs 20 mpg). Lately the price is about 18 cents a gallon higher for the ethanol-free which on $3.25 per gallon is about 5% more, so it's worth the trip dollar-wise plus the satisfaction of no worry about the ethanol is priceless.
There is all-too-serious talk of EPA raising the 10% ethanol up to 15 or 20%. 
As of now, at 10% poorer gas mileage, there is no savings on gallons of straight gas being used so that argument doesn't hold up. Seems all it adds up to is an indirect subsidy to corn growers. Can't see it being anything else.

[hardpan]

Higher octane does not make a fuel burn slower-

http://www.racegas.com/article/10

Thanks. Good little article. It answers a question I've had for a long time. I knew a higher octane resisted ignition by compression (like a diesel) but I was unsure about the burn rate once ignition occurred. I have used 100LL and like everything about it except the price, $5.35 a gallon last time I bought it. Yes, it evaporates fast and clean and the shelf life is way beyond the normal pump gas.

[mad murdock]

welcome to the forestry forum hardpan and scottman22!  As far as the cost of 100LL, one reason is the quantity used each year gets less and less, plus there is only one source for the tetraethyl lead additive left worldwide that I know of, a manufacturer in the UK, so that adds to the cost of it as well.  I would love to see someone sell non-additive gasoline, like you used to be able to buy back in the day, before they added all the benzene, tolulene, and whatever other solvents, scrubbers, etc.  It is all the aeromatics added to gas at the mogas pump that makes it varnish if left over time, not to mention the ethanol component which though will allow water absorption, robs power from the fuel, IMO. 

[sharkey]

From what Ive seen, AV gas will store in a tightly capped metal Jerry can for years and be good to go.  Cant say the same for MO gas.  Remember ethanol holds water.  The best thing you can do for your saw is to run it dry when your done using it.  I know this isnt practical for alot of users, but if your equipment is going to sit, drain it and run it dry.  It may take a couple more pulls to re-fire it, but it will always start this way.  Best practices dictate fresh fuel, nothing over 6wks old in a plastic can, always capped tightly and kept out of the sun.   

[RCBS]

I finally found a non-ethanol source this summer.  90 octane with no corn.  It's a twenty mile ride and is slightly more expensive, but the peace of mind is worth it.  ...........................

I use corngas in my truck as it is not practical to drive 20 miles to fill up, but I would for sure pay a premium to have pure gas available at all stations.  The truck gets an average of 2mpg better on pure gas.  ..............

/rant.

I drive almost 20 mile to the non-ethanol station.. as I also get 2 mpg better gas mileage. That is 10% more (18 mpg vs 20 mpg). Lately the price is about 18 cents a gallon higher for the ethanol-free which on $3.25 per gallon is about 5% more, so it's worth the trip dollar-wise plus the satisfaction of no worry about the ethanol is priceless.
There is all-too-serious talk of EPA raising the 10% ethanol up to 15 or 20%. 
As of now, at 10% poorer gas mileage, there is no savings on gallons of straight gas being used so that argument doesn't hold up. Seems all it adds up to is an indirect subsidy to corn growers. Can't see it being anything else.

The corn lobby be mighty strong these days.  Just give me a choice at the pump is all I'm asking.  I can choose from 3 different grades...all with ethanol.  How about two ethanol grades and one puregas.  As stated, I don't mind paying a premium as the milage increase negates the higher cost.

Phase separation

http://www.enertechlabs.com/fuel_phase_separation_in_ethanol.htm

And speaking of corn...

http://www.infowars.com/total-gmo-ban-to-be-considered-by-russia-within-weeks/

Summary:  I hate ethanol and corn syrup.   :D  IF we as consumers stop buying the stuff with this crap in it, companies will stop adding it into their products.  I'm already seeing the backlash against what is now called "corn sugar".  Many food packages proudly display "No high fructose corn syrup" on the packaging.  RCBS likes this!   

[weimedog]

I ran 100LL for a while, especially when I was milling with my old Homies & Macs. They ran ..cooler lol. Of course you all know why. I can get 100LL at the local airport. Advantages are as already articulated. Dissadvantages are priceand its a pain in the  to get. If I don't find a source of non ethanol laced fuel, I may go back to 100LL.  Until they find a way to safely fuel those old aircraft motors that are still flying......100LL will be around.

[SlimJim]

Here is a copy of tech tips from Rockett Race Fuels (the old Union76 people)



Myth: Street gasoline with oxygenates is junk.

Fact: Street gasolines of today, especially in California, are the best performance gasolines next to racing gasoline.

Myth: The higher the octane, the slower the burn.

Fact: In many cases, high octane gasoline has faster burning characteristics than low octane gasoline. It is rarely slower.

Myth: Too much octane reduces horsepower.

Fact: Trying a higher octane fuel and getting less performance is usually due to introducing additional variables with the different gasoline which can be overcome by re-tuning the engine.

Myth: Aviation Gasoline is a good substitute for racing gasoline.

Fact: Aviation Gasoline is designed for engines that run at 2700 to 2800 RPM at 10,000 feet. If your race engine runs under these conditions, then aviation gasoline is the hot tip.

[LaegersATC500R]

Do they mention  any thing about ethanol in the fuel myth?