Am I the last person to get this information, or do I just not read instructions as I should? I bought a new weed trimmer (Echo), and it ran super for a season. Starting this past season it basically stumbled and failed. New gas and 40:1 oil as recommended. So I was reading the book ( I know it isn't very manly) and it says it must have 89 octane or higher gasoline. Our regular gas in the South is 87. I was skeptical, but went and filled up all the gas and diesel cans yesterday and put 89 octane in the gas cans. I mixed up a new batch with oil, put it in the machine, and after a few pulls and choke "messing", it began to run perfectly.

Would that little octane change make such a difference??

 

Well, the higher the octane rating the higher the compression rating it can stand and you seem to have the proof.

Have never read my manuals but was planning to put my lawn tools/toys away today so I'll take a look at the manuals and see if there is anything similar.

 

I guess if it didn't make a difference they wouldn't sell 89 octane fuel. Sounds like the proof is in the puddin. I will also have to check my manuals. Now look what you have done!

 

I had a small engine guy tell me that you need to run hi test in small engines. I used to follow his advice but I'm more inclined to believe that non ethanol fuel is more important so that's what I've been using for the last number of years. There are several placeds that sell non ethanol regular but I only know of one that sells it in all grades - and it's more than twice as far from me.

Not sure where they are or if I've read the owner's manuals but everything runs good for me ..... knock on wood

 

The 87 octane is usually 10% ethanol, I'm assuming that is the difference. I've also heard not to use ethanol in small engines.

 

Our local small engine shop has a quart of regular gas sitting on his counter. It has about a quarter inch or more of non combustible ethanol residue in the bottom. You DON'T want that in your tank. I'm switching to non ethanol.

 

Ethanol is a type of alcohol. Since when is alcohol not combustible? I suspect the quarter inch on the bottom is water which ethanol will absorb.

https://en.wikipedia.org/wiki/Ethanol

That said, non-ethanol fuel will run better in small engines.

 

Ethanol is derived from corn. It does burn but not nearly as well as straight gas.
Ethanol is also what turns to corn syrup and clogs carburetors when the fuel evaporates.

 

I thought that was also "varnish" from gasoline. Either way it impurities in the fuel.

 

Tanks, carbs and fuel lines were getting gummed up with 'varnish' long before they started adding ethanol to the fuel. I always thought that evaporation had something to do with.

 

Either ethanol-mixed or non-ethanol fuel can leave varnish and residue but ethanol is hygroscopic. It want's to absorb water and will get it even from the air around it. This water will eventually bind with other stuff in the gas and separate. Then this reacts with the metals int he carb and makes different weird residues. I've pulled globs of jelly out, stuff that looks like tapioca pudding, etc...

On most air cooled engines, the lower octane fuel is recommended because it burns faster and may reduce temps a little because it fires sooner, where the preset fixed ignition timing has been optimized by the manufacturer. Firing sooner in a high compression engine can increase temps, but most small engines are lower compression and the higher octane fuel will fire later, increasing exhaust temps, reducing power, and having a similar effect to retarding the timing. That's my understanding of it anyway.

I don't think that your problem was related to the available octane in the fuel, I think it was coincidence, something else that got sucked into the carb maybe and flushed out, maybe some water? Even high compression engines can run decently on low octane fuel. The problem is that they will ignite early (like advancing the timing too far) and cause pre-ignition, which decreases power, increases temps, and ruins the pistons with long term use.

Low, mid, and premium gas can all have ethanol in them in varying amounts. Usually they can have UP TO 10%, but that doesn't mean they have 10%. They might be 5, 7, or whatever, but the pump says up to 10%. Ethanol has less energy than regular gasoline, so as the percentage of ethanol in the gas gets higher, the amount of work done (run time, miles traveled, etc...) will decrease proportionally.

Ethanol also attacks rubber, even some new rubber that is made to be used with ethanol.

I'm not a chemist or scientist, but this is my understanding of it all after being in the automotive trade and small engine business for the past 25-30 years.

 

Its the ethanol in the 87 fuel.
For the extra 10 cents, I use 93...

 

Just buy gas without ethanol. Have to look around for it but most towns have pumps with it. Will be posted no ethanol on pump.

 

That's all your price difference is between regular and high test? It's at least 30¢ locally. Ethanol free regular is about 50¢ more per gallon but I only use it in my small engines so the extra cost isn't bad.

 

A buddy of mine who works part-time at a local mower shop is adamant about using only non-ethanol in small engines. Pure-gas.org maintains a list of stations that carry non-ethanol.

 

The problem with ethanol is its properties which cause corrosion to metal and weakens plastic and rubber. For these reasons ethanol over 10% should be avoided. 10% ethanol is OK but should not be stored in the machine's tank over 30 days unless an additive us used.

Higher octane fuels are generally not needed except for 2-stage engines where the oil mix reduces the octane.

 

Does anyone have insight on using ethanol treatments in regular gas? Lucas Oil 5.25 oz. Safeguard ethanol fuel treatment 10670 - Read 1 Reviews on Lucas Oil #10670

Probably more expensive per capita than just buying ethanol free gas.

 

I don't use any additives in my vehicles and Sta-bil in my power equipment. My guess is that's pretty much the standard.

 

I always add StaBil to my last tank if the engine is going to set for an extended period. I generally add a fuel system cleaner to my vehicles every 5-10k. I've never used the ethanol treatment.

 

Mark, I also use Instead-o-lead in my 1955 Ford 840 tractor. I know today's fuel is rough on such an old engine.

 

If you read further in the manual and warranty, (Echo I know for sure as I recently declared a shred n vac deceased on warranty claim) it does state to use 89 octane or higher and no more than 10% ethanol. As far as I know, all Echo products should use a mix ratio of 50:1 as that is what their Power fuel premix is that is sold and also recommended.
Higher octane fuel will handle more compression before igniting/detonating and there fore actually runs a bit cooler than lower octane fuel.
I have had a saying for quite some time, "Real Men READ the instructions". Why re-invent the wheel when someone has already gone through the effort to inform you?
In the case of Echo's 5 year "Consumer/limited warranty, it mentions several things that warranty will not cover, and all of those issues are covered in the manual. This not only includes octane and fuel, but storage, spark plugs, maintenance....etc. In the case on the PB-250, it came in with unknown fuel, the wrong spark plug and no air filter and had been used for 4 seasons on several rental properties. The customer also mentioned possibly using some unknown or bad gas trying to get one job finished up.
The dealers are on the front line of this battle and only diagnose the issue for a warranty claim, the manufacturer is the one that determines whether or not the claim is valid. Even when a dealer honors a claim, they then must retain/return the equipment/parts and appease the manufacturer before receiving payment and are also only allowed a minimal labor charge derived from a tech who can do it blind folded, on new equipment, with all the specific tools in a clean room setting...

 

For years I always used instead of lead in my flathead V8. Back when they first quit selling leaded gas I read an article stating all the bad things that could happen to your valves with unleaded gas. 12-15 yrs later I read an article that debunked the first one. Haven't bought instead o lead since. Drove it many yrs without the additive. Haven't drove it in quite a few yrs, my 51 F1 sits patiently in the barn waiting for me to have time to put it back on the road. I always run 10% ethanol in my 53 NAA [same engine as your 840 - I think]. Haven't had any ethanol problems with my tractor in the 25 yrs I've had it.