Sunoco non ethanol fuels

[Tom123]

I saw this at the local Sunoco today. I read up on the Optima, sounds like it is good for small equipment. 3 year shelf life, 95 octane. Around $50 for a five gallon can. I'm thinking of using it in my saws, blowers, weedwacker, and generator. Any thoughts or experience?


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[Ashful]

Watching. I wonder, will saw tuning change much with the change in octane rating, assuming most are running 92 - 93 octane?

 

[WoodyIsGoody]

I saw this at the local Sunoco today. I read up on the Optima, sounds like it is good for small equipment. 3 year shelf life, 95 octane. Around $50 for a five gallon can. I'm thinking of using it in my saws, blowers, weedwacker, and generator. Any thoughts or experience?View attachment 199272

With a three year shelf life it must be loaded with stabilizers. I'm sure it will work but, once you mix a quality chainsaw oil with it, it's going to be doubled up on stabilizers Probably not a problem but since the formulas are proprietary, compatibility could also be an issue. My Stihl 026 has run flawlessly with one exception for over 20 years on nothing but 89 pump gas w/10% ethanol and 50:1 Stihl Ultra oil. However, I've switched this year to 90/91 octane non-ethanol pump gas and 50:1 Stihl Ultra. I also have a bit of Stihl Moto-mix that I will run during the slow season from now on to avoid draining.

Plenty of years that saw sat over the winter with a partial tank of ethanol and it always started and ran like clockwork. I think I could have avoided the $16 for a new fuel pick-up had I drained the fuel before putting it away.

 

[WoodyIsGoody]

Watching. I wonder, will saw tuning change much with the change in octane rating, assuming most are running 92 - 93 octane?

Probably, but not necessarily. It depends on the blend of distillates they use to achieve the octane. It's possible for a 95 octane gasoline to have exactly the same amount of embodied energy as a 89 octane fuel (which would require the same tuning). It's also possible for two fuels with identical octane to require different tuning. More often than not, Supreme grades have slightly lower amounts of embodied energy than Regular and require a slightly richer tuning and produce slightly less power. But this is probably not the case with the Optima since it's sold as a speciality/premium racing fuel. To me that implies it's blended from more energy dense distillates and would require a slightly leaner tuning to achieve a stoichiometric mixture.

I should add that the amount of oxygen in the fuel can also change the tuning requirements. The optima has none so that would indicate a leaner tuning as well.

The octane tells you very little about the fuel except for how resistant it is to detonation.

 

[Tom123]

With a three year shelf life it must be loaded with stabilizers. I'm sure it will work but, once you mix a quality chainsaw oil with it, it's going to be doubled up on stabilizers Probably not a problem but since the formulas are proprietary, compatibility could also be an issue. My Stihl 026 has run flawlessly with one exception for over 20 years on nothing but 89 pump gas w/10% ethanol and 50:1 Stihl Ultra oil. However, I've switched this year to 90/91 octane non-ethanol pump gas and 50:1 Stihl Ultra. I also have a bit of Stihl Moto-mix that I run during the slow season.

Plenty of years that saw sat over the winter with a partial tank of ethanol and it always started and ran like clockwork. I think I could have avoided the $16 for a new fuel pick-up had I drained the fuel before putting it away.

Back before ethanol (politically correct additive) pump fuel never needed stabilizers that I know of. You could let a vehicle or piece of equipment sit for years and the fuel system would be fine.


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[Tom123]

Probably, but not necessarily. It depends on the blend of distillates they use to achieve the octane. It's possible for a 95 octane gasoline to have exactly the same amount of embodied energy as a 89 octane fuel (which would require the same tuning). It's also possible for two fuels with identical octane to require different tuning. More often than not, Supreme grades have slightly lower amounts of embodied energy than Regular and require a slightly richer tuning and produce slightly less power. But this is probably not the case with the Optima since it's sold as a speciality/premium racing fuel. To me that implies it's blended from more energy dense distillates and would require a slightly leaner tuning to achieve a stoichiometric mixture.

The octane tells you very little about the fuel except for how resistant it is to detonation.

You are correct. What you are referring to is the BTU content of the fuel. BTU and octane rating are two different things. Most pump gas has the same BTU content across octane values. I am curious to see if anyone has experience with this particular fuel. I will probably pick up a 5 gallon can and mix saw gas 1 gallon at a time with Stihl Ultra.


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[WoodyIsGoody]

Back before ethanol (politically correct additive) pump fuel never needed stabilizers that I know of. You could let a vehicle or piece of equipment sit for years and the fuel system would be fine.

Either you are too young to know, or too old to remember (no offense meant). Yes, fuel stabilizers were needed and available long before alcohol was introduced to pump gas. In fact, Sta-bil fuel stabilizer was introduced in the 1960's to prevent gunked up carburetors and other problems of gasoline aging. I remember as a teenager and beyond, most car and motorcycle engine problems were caused by old fuel gumming up the carb(s) or water in the gasoline. Long before the "evil" alcohol was in the gasoline.

In fact, when an engine sputtered or ran rough or wouldn't start, the problem was often water in the fuel tank. Mind you, this was before ethanol formulated gasoline. Guess how we fixed it? We would go to the auto parts store, buy a 12 oz. bottle of pure alcohol (actually 95% alcohol, 5% water) and dump it in the fuel tank. This would almost always fix the problem. The same stuff that already makes up 10% of most pump gas. Really stubborn cases might need 2 bottles to be able to absorb all the water. You see, gas caps in the day were exposed to the weather and not as water-tight as they are today. And without alcohol in the gas, the water would phase separate and just collect down by the fuel pick-up.

"Phase separate", you say, "isn't that a problem caused by alcohol in the gas?". No. There are a lot of myths out there designed to make ethanol look worse than it is. Ethanol formulated gasoline is 100's of times less likely to phase separate than ethanol free gas. Pure gas, without alcohol, can only hold a miniscule amount of water before it phase separates. Just the normal condensation in a fuel tank only half full can collect enough water to separate from non-ethanol fuel. Ethanol fuel can absorb quite a bit of water and pass it out the tailpipe along with the normal moisture of combustion. Back in the day of ethanol free fuel, that's all the moisture it took to cause rough running or a no-start situation. Two bottles of "mechanic in a can/alcohol" were only needed if you had rainwater leaking in your tank.

How short our memories are (and how many urban myths are created and endlessly passed along).

 

[Tom123]

Either you are too young to know, or too old to remember (no offense meant). Yes, fuel stabilizers were needed and available long before alcohol was introduced to pump gas. In fact, Sta-bil fuel stabilizer was introduced in the 1960's to prevent gunked up carburetors and other problems of gasoline aging. I remember as a teenager and beyond, most car and motorcycle engine problems were caused by old fuel gumming up the carb(s) or water in the gasoline. Long before the "evil" alcohol was in the gasoline.

In fact, when an engine sputtered or ran rough or wouldn't start, the problem was often water in the fuel tank. Mind you, this was before ethanol formulated gasoline. Guess how we fixed it? We would go to the auto parts store, buy a 12 oz. bottle of pure alcohol (actually 95% alcohol, 5% water) and dump it in the fuel tank. This would almost always fix the problem. The same stuff that already makes up 10% of most pump gas. Really stubborn cases might need 2 bottles to be able to absorb all the water. You see, gas caps in the day were exposed to the weather and not as water-tight as they are today. And without alcohol in the gas, the water would phase separate and just collect down by the fuel pick-up.

"Phase separate", you say, "isn't that a problem caused by alcohol in the gas?". No. There are a lot of myths out there designed to make ethanol look worse than it is. Ethanol formulated gasoline is 100's of times less likely to phase separate than ethanol free gas. Pure gas, without alcohol, can only hold a miniscule amount of water before it phase separates. Just the normal condensation in a fuel tank only half full can collect enough water to separate from non-ethanol fuel. Ethanol fuel can absorb quite a bit of water and pass it out the tailpipe along with the normal moisture of combustion. Back in the day of ethanol free fuel, that's all the moisture it took to cause rough running or a no-start situation. Two bottles of "mechanic in a can/alcohol" were only needed if you had rainwater leaking in your tank.

How short our memories are (and how many urban myths are created and endlessly passed along).

I would bet I am older than you. I own a 65 Ford Falcon that has been in the family since new. I was with my grandfather when he picked it up at Stevens Ford in Milford CT. Before giving me the car in 1979 he would drive it less than 200 miles a year and there were times it would sit for an entire year. Fuel was never an issue. He would keep the tank near full to minimize condensation. I never even heard of STA BIL until 10-15 years ago. The ethanol additive you speak of is known as dry gas. You are correct. I have not needed dry gas since the addition of ethanol. My dad was a commercial pilot and flew mostly single engine small aircraft. We would always drain fuel from the bottom of the tank to check for water as part of pre flight check . There would almost always be some. 2 or 3 cups would drain it all off. Bottom line is the fuel we get today is not the quality we used to get. It even smells different.


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[WoodyIsGoody]

I would bet I am older than you.

I suspected you were older. Our memories are short relatively speaking. I've seen many motorcycle carbs completely varnished up from old gas (pre-ethanol). A very common problem. I have a theory that the "good ol' days" are mostly good because our memories are bad. That and good memories are more rewarding than bad ones.

Remember flat tires? I haven't had one in over 25 years. Remember lead in the gas? Back then we didn't have the Internet and most people didn't even know it could cause brain damage and developmental problems in your children at very low levels. We used to think it was sensible that car makers provided us with such soft valve seats that it was necessary to put toxic lead in the fuel supply just so their inferior/cheap valve seats wouldn't get mashed to mush. Now valve seats are precisely ground and made out of suitably hard metals so they last longer than the car. A valve job at 85,000 miles was considered normal (even with toxic lead in the gasoline). Why we put up with toxic chemicals just to allow shoddy metallurgy and cheap manufacture is beyond my comprehension. I guess because it was "the good ol' days" and we didn't know any better.

Yes, the good ol' days when a 7 second 0-60 mph was considered muscle car territory and a 5 second 0-60 was not even available. The good ol' days when suspensions were either wallowing like drunken pigs or transmitting every jolt in the road to your poor spine.

What I know about the combination of today's fuels and engines is that engines make more power, get better mileage, don't stink as bad and are far less toxic, emit far fewer greenhouse gasses, have longer range, need far less maintenance, last far longer and almost never break down. If the fuel is inferior to what I had in the '70's, I want more inferiority! I'm not gonna complain about how the gas isn't as good as the good ol' days. I want more of what we've been getting.

 

[Tom123]

I suspected you were older. Our memories are short relatively speaking. I've seen many motorcycle carbs completely varnished up from old gas (pre-ethanol). A very common problem. I have a theory that the "good ol' days" are mostly good because our memories are bad. That and good memories are more rewarding than bad ones.

Remember flat tires? I haven't had one in over 25 years. Remember lead in the gas? Back then we didn't have the Internet and most people didn't even know it could cause brain damage and developmental problems in your children at very low levels. We used to think it was sensible that car makers provided us with such soft valve seats that it was necessary to put toxic lead in the fuel supply just so their inferior/cheap valve seats wouldn't get mashed to mush. Now valve seats are precisely ground and made out of suitably hard metals so they last longer than the car. A valve job at 85,000 miles was considered normal (even with toxic lead in the gasoline). Why we put up with toxic chemicals just to allow shoddy metallurgy and cheap manufacture is beyond my comprehension. I guess because it was "the good ol' days" and we didn't know any better.

Yes, the good ol' days when a 7 second 0-60 mph was considered muscle car territory and a 5 second 0-60 was not even available. The good ol' days when suspensions were either wallowing like drunken pigs or transmitting every jolt in the road to your poor spine.

What I know about the combination of today's fuels and engines is that engines make more power, get better mileage, don't stink as bad and are far less toxic, emit far fewer greenhouse gasses, have longer range, need far less maintenance, last far longer and almost never break down. If the fuel is inferior to what I had in the '70's, I want more inferiority! I'm not gonna complain about how the gas isn't as good as the good ol' days. I want more of what we've been getting.

I realize I brought up cars but I started this thread talking about fuel for small carbureted engines. I agree cars are way better now. Electronic fuel injection, computer controlled timing and mixture etc. But the fact is ethanol fuel is corrosive to the small parts on power equipment including carb diaphragms, fuel lines etc. let's face it, as battery technology gets better we won't even need fossil fueled equipment, and as an electrical engineer I say bring it on.


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[WoodyIsGoody]

I realize I brought up cars but I started this thread talking about fuel for small carbureted engines. I agree cars are way better now. Electronic fuel injection, computer controlled timing and mixture etc. But the fact is ethanol fuel is corrosive to the small parts on power equipment including carb diaphragms, fuel lines etc. let's face it, as battery technology gets better we won't even need fossil fueled equipment, and as an electrical engineer I say bring it on.

Right on.

Materials that withstand alcohol are slightly more expensive. And while car manufacturers have made the switch, I guess the small engine manufacturers took their time. I attribute the one failure on my 20 year old chainsaw (cracked fuel pick-up line) directly to the ethanol laced gasoline. But it took 15 years of sitting in ethanol to crack. I would be willing to bet new Stihl saws use a fuel pick-up material that is more resistant to ethanol (my saw was built in 1996). I bet each fuel pick-up costs 3 cents more because of the change in materials.

In Brazil, the minimum alcohol in gas is 25% by law. Most "gas" stations offer different blends, right up to E100 (pure alcohol) and the new car industry responded by manufacturing engines/fuel systems that can run any blend from 20% ethanol right up to E100.

Brazil is the second largest producer of ethanol in the world (second only to the U.S.). While Brazil has a thriving oil industry, their domestic ethanol consumption allows them to export most of their oil for profit. This allows them to have a trade surplus instead of the trade deficit we have in the US. Of course trade deficits are complex things and oil alone did not get us there. But every little bit helps. U.S. ethanol production has greatly lowered our deficits and is a major reason why gas prices are lower than they were in the 1920's (adjusted for inflation). And that is why oil majors don't like ethanol and why they start myths about how bad it is for engines.Ethanol reduces demand for oil.

Do you really think working class Brazilians could afford to drive a car on e100 if it was bad for the expensive engine? Brazil is the "dirty little secret" oil companies don't want you to know about. They want you to believe alcohol is so corrosive that even 20% of it would be impossible to design for. Well, we have e85 right here. While gas offers definite advantages over e85 and e100 in terms of HP/cc and driving range/gallon fuel, vehicles running on e85 exclusively for years prove that it's not prohibitively expensive to outfit engines to handle alcohol. Most flex fuel vehicles never use e85 but it's cheap enough to build them to handle it that's not a problem.

Thankfully, lead is gone from our tailpipe emissions. Don't try to commit suicide with the tailpipe hose in the cabin/garage trick if running on e100. Because the exhaust is mostly water and carbon dioxide.

 

[Bad LP]

10 bucks a gallon! Holy 'ol dog bite. The non E10 91 octane gas at the marina where I slip my boat is only 3.85 this year. With a 150 gallon tank I'd cry.

Gas from years back had storage issues and it raised hell in all fuel systems if left to sit for long. How long has Gumout been for sale???

 

[Tom123]

10 bucks a gallon! Holy 'ol dog bite. The non E10 91 octane gas at the marina where I slip my boat is only 3.85 this year. With a 150 gallon tank I'd cry.

Gas from years back had storage issues and it raised hell in all fuel systems if left to sit for long. How long has Gumout been for sale???

$10 a gallon is quite a bit. Then again a quart of Moto Mix is $9.00 I have been looking around for ethanol free fuel in CT. The only thing I have found is this and VP racing fuel. I have not seen it at the marinas. I currently use Shell 92 octane pump gas with Stihl Ultra oil. I do run Moto Mix when I put the saw away for the week or whatever. I also like to put a quality fuel in my generator and not have to start it once a month or so, or drain it.


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[kenskip1]

My slight contribution to this mix is that the saws are designed to run on 87/89 octane.Now you toss this 93 in and what do you have? A saw that will not run to it's full potential. 93 octane is more difficult to ignite than 87.Granted that this will work but my method is using 89 pump gas with a dose of Amsoil and keep it in a Sealed container out of the hot sun.It has worked for me for over 15 years. ken

 

[peakbagger]

Unfortunately blended motor fuel is not really pure gasoline. Its actually a blend of several petroleum fractions. Every barrel of crude oil has a specific mix of petroleum fractions that yield different optimum mixes of different fuels. Early motor fuel pretty much was limited to the mix of fractions available in the crude being used. If the crude was "light" it tended to yield more motor fuel "gas" and less diesel. Heavy crudes tended to yield more heavy distillates like diesel. In the early automotive years gas engines were easier to build than diesels as a diesel has higher compression ratio and not very easy to crank start. The early US crudes tended to be light crude as it was easier to get out of the ground so the oil drillers grabbed the light stuff and left the heavy stuff in the ground. With autos demanding gas, the other fractions were in less demand and sold at a discount. The auto fuel blends were pretty stable as they were blended out of direct fractions from the distillation columns. If the fuel tanks are sealed the auto fuel lasts quite awhile. Unfortunately the vapor pressure of fuel changes as its heated and cooled and most tanks are designed to be vented. If a tank is vented be it a 5000 gallon tank or a automobile gas tank the high fractions of the fuel that contribute to high octane tend to boil off. Carbs have the same issues, they were vented to atmosphere so as the car sat the fuel evaporated away with the higher fractions going first. Folks attributed that to stale gas. Talk to any aircraft pilot and when they have to cache fuel they have it shipped and stored in sealed 55 gallon drums. That fuel stays good for years until its opened. I know of more than a few folks who run their trucks from fuel left over in the barrels that pilots have left.

At some point the oil refiners developed catalytic cracking, this let them take the heavier fractions and break them into lighter fractions which meant that they could take heavy fractions like asphalts, tars and diesels and turn them into higher fractions to make auto fuel. This bumped the yield of a barrel of crude way up and gave the oil companies a reason to pump heavier fractions of oil out of the ground. This was a major contributor to fuel costing less is the useful yield of barrel of crude has gone way up while the usable types of crudes have increased substantially. The tar sand folks take this to an extreme and they use syn fuel processes to break the bitumen down into something that can be refined.

Unfortunately the broken molecules from cracking and syn fuel processing like to recombine as they age. Combine that with the lighter fractions that boil off and you end up with modern motor fuel that goes bad quickly and leaves deposits that are the result of cracked molecules slowly recombining into where they came from. Since most fuel is turned over quickly we put up with the tradeoff as the alternative is far more expensive fuel and most likely an oil shortage.

Now add in alcohol to the mix, unlike the crude oil based fuels its not a hydrocarbon, it burns but it has a lower vapor pressure which means that if a fuel tank and carb bowl is vented, the hydrocarbon fractions boil off long before the alcohol boils off. That means that the longer the fuel remains in the carb like a seasonal engine, what is left is mostly alcohol mixed with lower fractions of gasoline. To further contaminate the blend, alcohol binds with water so the resulting fuel in the fuel bowl is closer to wet diesel and that's what clogs up the carburetor, thus the recommendation to run the fuel out on small engines. There are all sorts of additives that try to keep things in one blend but they wear out and storage is inherently difficult as rarely are storage tanks unvented so daytme heating and cooling slowly allows higher fractions to leave the mix.

There are long term storage fuels available, they are just custom blends of straight distillates that haven't been cracked and they sure don't include oxygenated additives like alcohol. They are also quite expensive and not rated for motor fuel use. Auto gas is a seasonal blend and fuel optimized for summer is far different than winter. Those hydrocarbons boiling off go somewhere and cause smog so auto gas has to be special blend to reduce this boil off, custom blended non motor fuels don't have to follow those regs. This coincidentally is the one plus for alcohol it displaces the higher fuel fractions for octane boosting. I expect the fuel in the original posting is probably a similar version using straight run uncracked components.

 

[WoodyIsGoody]

At some point the oil refiners developed catalytic cracking, this let them take the heavier fractions and break them into lighter fractions which meant that they could take heavy fractions like asphalts, tars and diesels and turn them into higher fractions to make auto fuel. This bumped the yield of a barrel of crude way up and gave the oil companies a reason to pump heavier fractions of oil out of the ground. This was a major contributor to fuel costing less is the useful yield of barrel of crude has gone way up while the usable types of crudes have increased substantially. The tar sand folks take this to an extreme and they use syn fuel processes to break the bitumen down into something that can be refined.

Unfortunately the broken molecules from cracking and syn fuel processing like to recombine as they age. Combine that with the lighter fractions that boil off and you end up with modern motor fuel that goes bad quickly and leaves deposits that are the result of cracked molecules slowly recombining into where they came from. Since most fuel is turned over quickly we put up with the tradeoff as the alternative is far more expensive fuel and most likely an oil shortage.

Large scale catalytic cracking was underway in the early 1940's. So to say that modern fuel goes bad quickly due to catalytic cracking, you would need to be comparing it to fuel before WWII.

Alcohol does increase the vapor pressure of pure gasoline but modern semi-sealed fuel systems and modern ethanol blended gas fares better than what we had in the 1970's. I'm not kidding, gummed up carbs were a huge issue long before ethanol hit the pumps. We have it much better today even if the fuel itself is slightly more volatile.

 

[WoodyIsGoody]

My slight contribution to this mix is that the saws are designed to run on 87/89 octane.Now you toss this 93 in and what do you have? A saw that will not run to it's full potential. 93 octane is more difficult to ignite than 87.Granted that this will work but my method is using 89 pump gas with a dose of Amsoil and keep it in a Sealed container out of the hot sun.It has worked for me for over 15 years. ken

Octane rating is a measure of how easily fuel will pre-detonate, once you have a spark even 95 octane will ignite just fine. Stihl Moto-mix is designed as an optimal fuel for chain saws and other power tools. It's 93 octane.

 

[mountainlake]

For equipment used often I'd just run ethonal laced fuel and put in that race fuel the last couple of tanks, if just used a couple of times a year I'd use it all the time.. Everyone should know how or learn how to tune a 2 cycle engine, it will save you a lot of money and you wont burn them up as you know when they are lean. Steve

 

[Ashful]

For equipment used often I'd just run ethonal laced fuel and put in that race fuel the last couple of tanks, if just used a couple of times a year I'd use it all the time.. Everyone should know how or learn how to tune a 2 cycle engine, it will save you a lot of money and you wont burn them up as you know when they are lean. Steve

My local saw shop sells Stihl non-ethanol pre-mix, but even as the seller, they say it's just too expensive to run. They sell it primarily for storage, and recommend you just run a tank thru your 2-stroke at the end of each season. Interesting way of balancing the cost/benefit of that product.

 

[redktmrider]

We have Rickers Fuel Centers here in Indiana, the one closest to me sells Lucas Oil 91 octane ethanol free gas for about $3.60 a gallon, much cheaper than the $20 a gallon premix at the stores, even with buying the Stihl oil.

 

[Jan Pijpelink]

Unfortunately blended motor fuel is not really pure gasoline. Its actually a blend of several petroleum fractions. Every barrel of crude oil has a specific mix of petroleum fractions that yield different optimum mixes of different fuels. Early motor fuel pretty much was limited to the mix of fractions available in the crude being used. If the crude was "light" it tended to yield more motor fuel "gas" and less diesel. Heavy crudes tended to yield more heavy distillates like diesel. In the early automotive years gas engines were easier to build than diesels as a diesel has higher compression ratio and not very easy to crank start. The early US crudes tended to be light crude as it was easier to get out of the ground so the oil drillers grabbed the light stuff and left the heavy stuff in the ground. With autos demanding gas, the other fractions were in less demand and sold at a discount. The auto fuel blends were pretty stable as they were blended out of direct fractions from the distillation columns. If the fuel tanks are sealed the auto fuel lasts quite awhile. Unfortunately the vapor pressure of fuel changes as its heated and cooled and most tanks are designed to be vented. If a tank is vented be it a 5000 gallon tank or a automobile gas tank the high fractions of the fuel that contribute to high octane tend to boil off. Carbs have the same issues, they were vented to atmosphere so as the car sat the fuel evaporated away with the higher fractions going first. Folks attributed that to stale gas. Talk to any aircraft pilot and when they have to cache fuel they have it shipped and stored in sealed 55 gallon drums. That fuel stays good for years until its opened. I know of more than a few folks who run their trucks from fuel left over in the barrels that pilots have left.

At some point the oil refiners developed catalytic cracking, this let them take the heavier fractions and break them into lighter fractions which meant that they could take heavy fractions like asphalts, tars and diesels and turn them into higher fractions to make auto fuel. This bumped the yield of a barrel of crude way up and gave the oil companies a reason to pump heavier fractions of oil out of the ground. This was a major contributor to fuel costing less is the useful yield of barrel of crude has gone way up while the usable types of crudes have increased substantially. The tar sand folks take this to an extreme and they use syn fuel processes to break the bitumen down into something that can be refined.

Unfortunately the broken molecules from cracking and syn fuel processing like to recombine as they age. Combine that with the lighter fractions that boil off and you end up with modern motor fuel that goes bad quickly and leaves deposits that are the result of cracked molecules slowly recombining into where they came from. Since most fuel is turned over quickly we put up with the tradeoff as the alternative is far more expensive fuel and most likely an oil shortage.

Now add in alcohol to the mix, unlike the crude oil based fuels its not a hydrocarbon, it burns but it has a lower vapor pressure which means that if a fuel tank and carb bowl is vented, the hydrocarbon fractions boil off long before the alcohol boils off. That means that the longer the fuel remains in the carb like a seasonal engine, what is left is mostly alcohol mixed with lower fractions of gasoline. To further contaminate the blend, alcohol binds with water so the resulting fuel in the fuel bowl is closer to wet diesel and that's what clogs up the carburetor, thus the recommendation to run the fuel out on small engines. There are all sorts of additives that try to keep things in one blend but they wear out and storage is inherently difficult as rarely are storage tanks unvented so daytme heating and cooling slowly allows higher fractions to leave the mix.

There are long term storage fuels available, they are just custom blends of straight distillates that haven't been cracked and they sure don't include oxygenated additives like alcohol. They are also quite expensive and not rated for motor fuel use. Auto gas is a seasonal blend and fuel optimized for summer is far different than winter. Those hydrocarbons boiling off go somewhere and cause smog so auto gas has to be special blend to reduce this boil off, custom blended non motor fuels don't have to follow those regs. This coincidentally is the one plus for alcohol it displaces the higher fuel fractions for octane boosting. I expect the fuel in the original posting is probably a similar version using straight run uncracked components.

Being a petroleum chemist, I can agree with most of the above. If somebody is interested how gasoline is made, let me know.

 

[WoodyIsGoody]

My local saw shop sells Stihl non-ethanol pre-mix, but even as the seller, they say it's just too expensive to run. They sell it primarily for storage, and recommend you just run a tank they your 2-stroke at the end of each season. Interesting way of balancing the cost/benefit of that product.

That's a good way to do it if you don't want to drain the machine dry seasonally because Stihl Moto-mix is more stable than typical non-ethanol pump gas mixed with Stihl Ultra. But I would also be comfortable only using non-ethanol pump gas mixed with Stihl Ultra (because it's stabilizers are good for most peoples seasonal storage needs). Probably more important than the exact fuel used (or combination of fuels) is to store the saw in a cool place that never gets too warm and doesn't have large day/night temperature swings. If you don't have that then it's a good idea to err on the conservative side with fuel (either drain it or use a premium canned/stabilized 2-stroke mix like Moto-mix). Cold, dry storage is best, right down to just above the freezing point, as long as the humidity is non-condensing. Cold temperatures reduce the vapor pressure of the fuel and thus the evaporation.

When using pump gas, the more regulated summer blend degrades more slowly than the winter blend with it's higher percentage of butane. Even if you live in a state that doesn't have more strict summer season vapor pressure limits, you might still get the more expensive, lower vapor pressure "summer" blend due to refinery and transportation logistics. So if possible buy your fuel before the summer standards are relaxed for winter. In general, at the retail level, summer blends are June 1-Sept 15 (but there is some mixing of grades both at the wholesale and retail levels during changeovers). In California the summer blend season is longer.

 

[WoodyIsGoody]

Being a petroleum chemist, I can agree with most of the above. If somebody is interested how gasoline is made, let me know.

I know a number of petroleum engineers but I've never heard any of them refer to themselves as "petroleum chemists" (although they all have degrees in organic chemistry). Is there a difference?

 

[Jan Pijpelink]

I know a number of petroleum engineers but I've never heard any of them refer to themselves as "petroleum chemists" (although they all have degrees in organic chemistry). Is there a difference?

Engineers are people involved with the production process. Chemists are the lab people, doing the analyses of the various products.

 

[WoodyIsGoody]

Engineers are people involved with the production process. Chemists are the lab people, doing the analyses of the various products.

Thank-you. I live in a town with two major oil refineries and one small specialty refinery and even the people in the lab doing quality control refer to themselves as "petroleum engineers".

You would think we would have some of the cheapest gas in the state but it seems to get less expensive the more distant you go from the refineries. Go figure! Even the petroleum engineers I know can't explain this odd fact to me (nor do they try to pretend they understand it).