# Gasoline question



## paratrooper (Feb 1, 2012)

I'm hoping that someone on this forum can school me a little on the octane in gasoline. 

In my area, it's next to impossible to find any non-ethanol gasoline. I have some high-end STIHL outdoor power equipment that requires gas and oil mix at a ratio of 50:1. 

I found a somewhat local source that sells racing gasoline. It is unleaded, non-ethanol and is 100 octane. It's $10.00 a gal. I can buy pre-mix gas / oil in 32 oz. cans at places like Home Depot, Lowe's and STIHL dealers, but it runs anywhere from $7.00 - $8.00. That ends up being over $32.00 a gal. 

Can anyone school me on octane and what part in plays in combustion and knocking? I was told at one time, that the higher the octane rating, the higher operating temps. it generates in engines. I don't know if that's true or not. 

I prefer to use non-ethanol gas for my pre-mix. Problem is, it's just not available where I live. Is 100 octane gas too much octane for use in pre-mix fuel? 

TIA! :smt1099


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## 92td (Jul 17, 2013)

Assuming that you are talking about a two stroke engine, they use an oil/gas mix and don't have any way except the oil in the gas to keep them cooled down, if you use higher octane gas it could potentially overheat and lock up, or start eating bearings and then your out a motor and those aren't cheap. I would just run pump gas from your local gas station and mix it with stihl two-stroke oil, or just some regular two-stroke oil. today's new engines can handle it.

Edit: that kind of racing gas is usually used in like two stroke dirt bikes, four wheelers, etc..


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## Philco (Apr 17, 2012)

I'm not sure what sort of high end equipment you are referring to but I've operated Stihl chainsaws and string trimmers for years using regular unleaded gas (87 octane) and Stihl two cycle oil mixed to manufacturers specs and have never encountered a fuel related issue. I know at least some of the fuel I used contained ethanol. I would think if you follow the owners manual instructions you'll be fine. I seriously doubt that the ethanol blended fuel is going to present any problems. If you're still not comfortable using it, why not contact the company and see what they can tell you ?


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## paratrooper (Feb 1, 2012)

Thanks for the replies. Yes, I'm talking about two-stroke engines, and I should have stated that out right. 

I have both conventional two-stroke oil and full-synthetic oil (Stihl Ultra HD) for use in the mix. I haven't had any issues with pump gas in the past, as I empty the fuel tank after each use, and then idle them dry until they stop. I'm talking about a chainsaw and a new line trimmer. 

As I mentioned, I can buy the pre-mixed canned fuel, but it's pricey. I just thought that if I could find some local non-ethanol gas, I'd go with that. But, it's no where to be had.


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## high pockets (Apr 25, 2011)

One of the biggest issues with ethanol in gasoline was that the ethanol tended to loosen particulates in fuel systems and clog up fuel filters. That is pretty much old school now. With the modifications to gasoline engines in the last 10 years, that is no longer an issue. 

I agree with those who are telling you to use regular fuel along with the manufacturer's recommended oil. The only issue you may encounter is that you may have to replace, or clean, your fuel filter/screen a little more often. Since the manufacturer usually never suggests a specific time for cleaning or replacing the filters or screens, you will probably never notice a difference.

If you feel very adventurous, contact Stihl and ask them.

ps: To stay with the theme of the forum, I must say I have never seen a gasoline fueled firearm, and would be a little concerned about carrying a flask of fuel concealed.


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## Cait43 (Apr 4, 2013)

high pockets said:


> ps: To stay with the theme of the forum, I must say I have never seen a gasoline fueled firearm, and would be a little concerned about carrying a flask of fuel concealed.


The poster did stay within the requirements of the forum by posting in the "General Discussion" thread which states:
*
General Discussion
Area for general off topic discussion. Please follow forum guidelines.
*


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## almanor (Jun 15, 2013)

ps: To stay with the theme of the forum, I must say I have never seen a gasoline fueled firearm, and would be a little concerned about carrying a flask of fuel concealed. 

What never seen a gasoline spud gun. We used to make them as kids. VBG. To answer the original post, The ethanol fuel won't harm your two strokes however it will go bad very quickly. If you don't use the fuel in a couple of months dispose of it and start fresh. Also running the engine dry may help or may make things worse if a small amount of fuel is left to dry out/form varnish. I'm now using a fuel stabilizer (sea foam) and changing out the fuel for small engines of all types every month of use. HTH.


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## paratrooper (Feb 1, 2012)

almanor said:


> ps: To stay with the theme of the forum, I must say I have never seen a gasoline fueled firearm, and would be a little concerned about carrying a flask of fuel concealed.
> 
> What never seen a gasoline spud gun. We used to make them as kids. VBG. To answer the original post, The ethanol fuel won't harm your two strokes however it will go bad very quickly. If you don't use the fuel in a couple of months dispose of it and start fresh. Also running the engine dry may help or may make things worse if a small amount of fuel is left to dry out/form varnish. I'm now using a fuel stabilizer (sea foam) and changing out the fuel for small engines of all types every month of use. HTH.


The oil I use for the pre-mix has stabilizers in it. I only mix up one gal. at a time, in plastic gas jugs only. After use, the remaining fuel gets dumped back into the gas jug, and I then start the machine back up and run it at idle until it dies on it's own.

In the past, I've been using 87 octane pump gas and it's never been an issue for me. But, I'm gonna start using 91 octane or higher (95 max. around here). The ethanol wasn't an issue for me until I started listening to what others had to say about it and what it does to small engines.

Some have said that it ruined an engine of theirs and others have said that it eats away at fuel / vacuum lines, seals, etc. And supposedly, unless properly stored, it draws moisture from the air.

Anyways, I feel that I'm doing things right and will continue to do so.


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## jdeere9750 (Nov 28, 2008)

What about avgas (100LL) for your 2 stroke engines?


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## paratrooper (Feb 1, 2012)

jdeere9750 said:


> What about avgas (100LL) for your 2 stroke engines?


I've had a few guys tell me to try it. But, it'd be a hassle to drive out to the airport to buy it and I think it's pretty pricey.

Overall, the general consensus is to just buy reg. pump gas (90 octane or higher) and use premium two-stroke oil.


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## johnr (Jun 13, 2008)

another place to check for non-ethanol fuel may be at a Marina, any Lakes nearby? Ethanol in boat engines has been a big controversy in the past few years. some boats had fiberglass fuel tanks and the alcohol fuel caused the fiberglass to deterioate, and the phase seperation during long storage periods added addithon failures from fuel lines to engine parts. Some local gas stations near lakes have started carrying either mid-grade or high grade just for the boaters.

ymmv

john


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## jdeere9750 (Nov 28, 2008)

paratrooper said:


> I've had a few guys tell me to try it. But, it'd be a hassle to drive out to the airport to buy it and I think it's pretty pricey.
> 
> Overall, the general consensus is to just buy reg. pump gas (90 octane or higher) and use premium two-stroke oil.


I think Sta-Bil makes a stabilizer for ethanol gas. Might give that a look if you haven't already.


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## paratrooper (Feb 1, 2012)

jdeere9750 said:


> I think Sta-Bil makes a stabilizer for ethanol gas. Might give that a look if you haven't already.


I have some Sta-Bil, but it's not all that new. Unless the company has come out with some new stuff that counter-acts the ethanol, all it does is prolong the shelf life of the fuel.

But, I'm gonna do a search on it and see what I can find out.

Found it: http://www.goldeagle.com/brands/stabil/


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## paratrooper (Feb 1, 2012)

johnr said:


> another place to check for non-ethanol fuel may be at a Marina, any Lakes nearby? Ethanol in boat engines has been a big controversy in the past few years. some boats had fiberglass fuel tanks and the alcohol fuel caused the fiberglass to deterioate, and the phase seperation during long storage periods added addithon failures from fuel lines to engine parts. Some local gas stations near lakes have started carrying either mid-grade or high grade just for the boaters.
> 
> ymmv
> 
> john


Yes, I have considered checking out a marina. I think we have one, but it's a way away, and out of the way. I'll make some calls tomorrow and see what I can find out.

Thanks for the reminder. :smt023


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## rex (Jan 27, 2012)

DO NOT RUN AV-GAS (aviation) IN A 2 STROKE!Please don't.Av-gas runs hotter than sub 100 octane and it seems to me doesn't hold the oil in suspension as well.When I rode motocross a few people tried this and it melted down the top ends beyond repair,and it was normal to at least re-ring or bore a motocross bike at least every few months of use.

All the oil is doing is lubricating the engine just like a 4 stroke engine does,the difference is the gas and oil are sucked into the bottom end through the reed valve on the piston up stroke causing a vacuum,then as the piston goes down it pumps the gas into the chamber for combustion.Some oil remains suspended,hence the smoke,but the majority clings to the bearings and metal in the bottom end.2 strokes make HP,not torque,compared to a 4 stroke,and they are designed to operate not sitting level like a car or lawnmower.If there was a sump for oil like a 4 stroke the crank would be slamming in the oil on rotation and if you turned it far enough it would pump oil into the chamber and smoke even more,fouling the plugs quicker.The remaining oil in 2 stroke oil is what causes the fouled plugs,just as a broken ring in a 4 stroke does.I always ran NGK plugs in 2 strokes because they handled it better,Champions didn't handle it well at all.

Normal 87 or 89 octane and good oil will be just fine,the less ethanol the better.Ethanol sucks up moisture just like brake fluid,that's why older guel systems needed rebuilt more often.The newer seals handle that better but it will still corrode aluminum parts.If it's going to sit idle,drain the gas and run the carb dry.If you use it weekly or more don't worry about it.Small 2 stroke engines have very small ports in the carbs and every few years they should be rebuilt anyway to get rid of the varnish that accumulates from the small amounts of gas that doesn't get burned out trying to run it dry.Fuel/air ratio is more critical with these than a 4 stroke,there's a fine line between running right,too rich or a meltdown from too lean.

A great oil if it still exists is TF580,I bought it for $30 a gal in the late 70s/early80s.Dirtbikes ran about 50-1 also but this could go about 60-1,and my worked over dirtbikes (snowmobiles,what-have-you) could run 72-1.I ran the latter and had great performance and a little longer time between rebuilds.


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## paratrooper (Feb 1, 2012)

rex said:


> DO NOT RUN AV-GAS (aviation) IN A 2 STROKE!Please don't.Av-gas runs hotter than sub 100 octane and it seems to me doesn't hold the oil in suspension as well.When I rode motocross a few people tried this and it melted down the top ends beyond repair,and it was normal to at least re-ring or bore a motocross bike at least every few months of use.
> 
> All the oil is doing is lubricating the engine just like a 4 stroke engine does,the difference is the gas and oil are sucked into the bottom end through the reed valve on the piston up stroke causing a vacuum,then as the piston goes down it pumps the gas into the chamber for combustion.Some oil remains suspended,hence the smoke,but the majority clings to the bearings and metal in the bottom end.2 strokes make HP,not torque,compared to a 4 stroke,and they are designed to operate not sitting level like a car or lawnmower.If there was a sump for oil like a 4 stroke the crank would be slamming in the oil on rotation and if you turned it far enough it would pump oil into the chamber and smoke even more,fouling the plugs quicker.The remaining oil in 2 stroke oil is what causes the fouled plugs,just as a broken ring in a 4 stroke does.I always ran NGK plugs in 2 strokes because they handled it better,Champions didn't handle it well at all.
> 
> ...


Good info. and thanks! :smt023


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## mallardhunter (Apr 9, 2013)

I have a 16 year old echo weed eater & echo chain saw I use only echo premium 2 cycle oil and regular pump gas. Never a problem in 16 years. I would use stilhl premium oil. The fuel stabilizers are built in.


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## paratrooper (Feb 1, 2012)

mallardhunter said:


> I have a 16 year old echo weed eater & echo chain saw I use only echo premium 2 cycle oil and regular pump gas. Never a problem in 16 years. I would use stilhl premium oil. The fuel stabilizers are built in.


I had a Stihl FS-44 weed eater. I bought it new in Aug. of 1998 for $200.00

I fueled it exactly the way you mentioned above and never had an issue. I kept it in such good condition, that I was able to sell it on CL for $125.00. I then took that money and applied it towards the Stihl weed eater (FS-250R) that I currently have. *BIG *difference in power......and money.

Think I'll just stick to pump gas (high octane) and Stihl ULtra HD full synthetic pre-mix oil. :smt023


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## rex (Jan 27, 2012)

Stihl makes top notch stuff,some of the best chainsaws on the market.They are high priced because they are professional grade compared to your everyday homeowner's needs.When I was a kid I turned wrenches for a Snapper/Ariens/Stihl and Echo dealer,the Ariens and Stihl were top of the line stuff.I did buy an Echo weedeater for my Grandfather then and it was a good piece of machinery.

You guys are right about the newer oils having stabilizers in them,much better than 30-40 years ago.97 octane is fine for these,just don't go higher because you won't see a difference.Cam2 was run in some of the dirtbikes and worked quite well,it was hard on them but not like Av-gas.The important thing is use good oil and don't let it sit in there too long and you'll get great service out of them.Also don't heat sink them,like cutting a small bit and shutting it down until you walk to the next light job,etc,and so on.The cooling comes from the flywheel fins and every time you shut it down it retains heat.If you do this a few times you;ll notice it gets finicky about restarting,it's overheating and tolerances are tightening up just like a car does when you run it out of water.They run but sluggish,because the rings and cylinder are are getting a years worth of wear in short order.

Hope this helps.


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## pic (Nov 14, 2009)

STIHL makes great demo saws also.
Your commercial/ industrial, building contractors all use STIHL.
Sometimes they go other then a STIHL, but learn very quickly.


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## paratrooper (Feb 1, 2012)

I come from a family with a long line of relatives working in the timber industry at one time or another. STIHL has been the choice when it came to chainsaws. 

I know Husky makes some good equipment, but I just don't know enough about them to want one. STIHL does make homeowner and mid-range equipment, but for a few extra bucks, you can buy the pro stuff. In the long-run, buying the pro stuff pays off.

Never ever thought I'd be in the right frame of mind to pay close to $600.00 for a chainsaw, let alone a weed-eater. But, I now own both.


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