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Non-ethanol chainsaw fuel debate

2 plastic fuel containers sitting on a worm bin with hay field in background

We wanted to cut down trees today for the new pig pasture, but ran out of fuel.

There's a gas station 10 miles away, but they put ethanol in their product.
older Stihl chainsaw closeup
It turns out the closest ethanol free station is 20.1 miles away. I debated just getting some higher octane gas at the nearby station to save time, but decided against it since our Stihl MS-211 is only 2 years old and might be more vulnerable to the negative effects of ethanol.

Our local mechanic has a chainsaw that's 15 years old and he uses regular fuel with no problems, but agrees that the newer chainsaws might need to stay away from ethanol.



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When I got my brand new Pro Dolmar saws a couple years ago, I looked everywhere for ethanol free fuel. Even the marina's near me don't have any. So I have been using regular but with every mix I put a good helping of Stabil fuel stabilizer in. Also using Stihl Full synthetic oil.

Just try and not have the mix older than 2-3 months and should be good.

Comment by Marco Tue Mar 26 17:57:46 2013
regular fuel is fine. just run it completely dry before storing. Do not store fuel with ethanol in a chainsaw or any other gas powered tool.
Comment by Anonymous Tue Mar 26 19:12:01 2013

Mark, Having been in the small engine field for over 20 years, I have been involved in many seminars and webinars on this subject. Basiclly what we have now(E-10) is borderline safe with Stabil or one of the many brands of additives. However, the E-15 that is coming is going to be the death of many small engines. The future of 2 -stroke engines in particular look gloomy.Stihl dealers offer premixed fuel in 1/2 gal containers now, but the price is more than most folks care to pay, for the time being.

Comment by Mike Tue Mar 26 19:17:48 2013

The main drawbacks of gasohol are that the EtOh theoretically can increase oxidation rate of plastic & rubber parts it may come in contact with, and that it can absorb water when allowed to sit. As mentioned above, just drain it out when storing the machine.

Higher octane gasoline actually has less "power" in it than lower octane gas, but because it has less of a tendency to pre-detonate under compression, it is used in higher compression engines- which are capable of squeezing more power out of the fuel. Don't waste your money on "premium."

It also might be pointed out how utterly stupid it is to turn food into fuel: 10% gasohol, by coincidence, also gives us 10% lower gas mileage. So, if it takes 1 gal of octane to go 20 miles, then it takes 1.1 gal of 10% mix to go 20 miles. This would seem like a savings of 1 gal of gasoline for every 100 gal of gasohol used, but it takes about 1 gal of petrol-based fuel to make the 1 gal of EtOH. Not to mention that, if our current supply of petroleum will last 100 yrs, then getting the whole world to use gasohol would make the supply last 101 yrs. BFD.

Comment by doc Tue Mar 26 21:33:33 2013

Personally I don't think it would be a bad thing crankcase-scavenged carburated two-stroke engines finally bit the dust. It might finally force manufacturers to improve on them!

In a study from a city in India where you still have lots of two-stroke scooters and motorcycles, 48% of non-smoking adults were found to have reduced lung function due to pollution.

Direct gasoline injection would reduce the pollution of a two-stroke engine significantly and would also reduce the fuel consumption (no more scavenging losses). It would also prevent problems with ethanol in the fuel attacking the seals in the engine and/or gathering in the bowl of the carburetor. Envirofit.org in the Philippines developed a kit for converting two-stroke motorcycles to direct injection, which worked very well. (But then the Philippine government mandated that all new motorcycles should have four-stroke engines and the market deminished rapidly...)

Replacing crank-case scavaging by an crankshaft-driven blower would further prevent the combustion air from picking up oil as well, and could give a significant power boost (acting as a supercharger) as well.

Large ship engines are usually externally-blown direct-injection Diesel two strokes. They can reach efficiencies of 50%, which is very high for an internal combustion engine.

Comment by Roland_Smith Wed Mar 27 15:54:42 2013
Really? And how do you propose to pressurize the fuel in a grass trimmer enough for direct injection? Fuel pumps and a battery? I do not need my trimmer any heavier and with yet another disposable maintenance item to take care of (battery,fuel filter and injector). Carburetors are not evil. Venturi effect has taken us this far, do not dismiss it just yet for small engines. Besides, a huge leap in efficiency was accomplished in the late 70's early 80's in carburetion efficiency. And then right on queue, oil got cheap again, and electronic systems finally catched up thus ending continued research in carburetion efficiency. That is called progress, yes, but note how you do not see fuel injected chainsaws... Nor electric ones worthy of a 12 inch tree either.
Comment by pedro Fri Mar 29 23:36:27 2013

I got carried away in my soapbox on the previous comment and forgot to write the most relevant part to the discussion: I bought a home depot poulan pro 18in chainsaw to clear 2 acres of old overgrown mesquite. I use e10 gas in it because that's what available, and it still starts right up every spring. Like other posters have written, I do empty it out after every use. And use a stabil in all my fuel. I have mistreated that sucker, like the inexpensive chainsaw it is, no maintenance to speak of, and yet it still starts every time. Old Mesquite is hard on the chains though, but that is not ethanol's fault....

Comment by pedro Fri Mar 29 23:47:32 2013

@Pedro: It is not the carburetor that is the problem. It is the combination of the carburated engine with crankcase scavenging. This means that the fuel/air mixture must push the exhaust gasses out of the cylinder. This leads more or less inevitable to scavenging losses; exhaust gasses remaining in the cylinder and unburnt fuel going out of the exhaust. And it also inevitably leads to the engine burning lubricant (because it's mixed into the fuel).

The solution to fuel loss is to scavenge with pure air. The solution to not burning oil is not not use the crankcase as the scavenging pump. Hence direct injection and external blower.

Direct injection is a solved problem. Diesel engines were the first to have mechanically driven injection pumps long before modern engine management systems were even possible. And it was also used in regular gasoline engines as early as 1907. These days, unit injectors are more popular. To the best of my knowledge, apart from fuel filters, these systems have no disposable parts.

Comment by Roland_Smith Sat Mar 30 08:44:16 2013

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