?? About octane for mowers and chain saw

[AlbertC]

I have a Stihl chainsaw and weed eater that the owners manual says to use 89 octane. I also have a John Deere mower that the manual says to use 87 octane. I have been purchasing non ethanol gas for each of these octanes at a cost of about $1 a gallon more. I have been using the non ethanol because I understand that it is much better for these Engines than using gas with ethanol in it.

Recently a new station started selling non ethanol but only in 90 octane. My question is would it be OK to use this 90 octane in my mower even though it only call for 87 octane or am I going to eventually encounter a problem with using this gas. Same question for the chainsaw, is it OK to use 90 octane when the manual calls for 89 Octane.

Thanks

 

[AlbertC]

I forgot to mention that the new station sells their non ethanol for about $1 less per gallon than the old store.

 

[Fastball]

Meh....regular gas and a 50:1 ratio.

 

[Wolfy]

Where I live, non ethanol gasoline is not sold. But either way, you want the highest octane you can get. Plenty of people will tell you that 87 octane is fine. Well Bullxxxt it is. I ran my Husqvarna 357XP on 87 octane and smoked the piston. Changed to 91 octane and never had another issue.

 

[KYErik]

Its fine to burn higher octane than is recommended- the recommended values are minimums. If the octane is too low for the application, you can get pre-ignition/detonation which can damage a piston/cylinder.

 

[motownbrowne]

90 will be fine. Ethanol free is definitely better. These small engines aren't high enough compression to warrant higher octane use, but it won't hurt them.

 

[motownbrowne]

Where I live, non ethanol gasoline is not sold. But either way, you want the highest octane you can get. Plenty of people will tell you that 87 octane is fine. Well Bullxxxt it is. I ran my Husqvarna 357XP on 87 octane and smoked the piston. Changed to 91 octane and never had another issue.

I really doubt that it was the octane rating that caused it. Thousands of chainsaws are run every day on 87 octane. It could have been a hundred other things, but just the octane seems really unlikely. 91 and 87 really aren't that much different.

 

[Wolfy]

The octane was the only variable that changed in my case.

 

[marchanna]

Octane is the measure of ignition delay. The higher the octane, the more the fuel can be compressed before it ignites. For best performance and reliability, you should use the octane that the engine is designed for. Using too low and you will get pre-ignition (knock), using too high and you will have lost power (higher octane fuel actually has less energy in it). Contrary to what some believe, higher octane is not synonymous with better fuel.

Ethanol blended fuel can damage seals and gaskets on older equipment, and is generally less stable, but is not poorer quality or cheaper fuel. Ethanol also has lower energy content than petroleum-based gas: about 10% less. At 10% blend, there is about 1% less energy overall - hardly noticeable.

 

[4570Man]

I run 87 octane in all of my small engines because it's the only gas I can get.

 

[fried1765]

I have a Stihl chainsaw and weed eater that the owners manual says to use 89 octane. I also have a John Deere mower that the manual says to use 87 octane. I have been purchasing non ethanol gas for each of these octanes at a cost of about $1 a gallon more. I have been using the non ethanol because I understand that it is much better for these Engines than using gas with ethanol in it.

Recently a new station started selling non ethanol but only in 90 octane. My question is would it be OK to use this 90 octane in my mower even though it only call for 87 octane or am I going to eventually encounter a problem with using this gas. Same question for the chainsaw, is it OK to use 90 octane when the manual calls for 89 Octane.

Thanks

Several responses state that non ethanol gas is not available.
That is not quite factually correct.
You can buy non ethanol (100LL) at any airport, in any state, in the USA.
I use it in my 8N, my gas Ford 3400, and mowers, generators, and saws.
It also stores much better than regular automotive gas.
One thing though: It is NOT CHEAP.
Local fire departments use it in all their small engines, because automotive non ethanol is banned in my (liberal) state.

 

[motownbrowne]

The octane was the only variable that changed in my case.

In my opinion that's not possible. You could have had 87 octane that was contaminated with water or was stale. Obviously when the octane changed so did the batch of fuel and I think we can include a new dose of mix. Right there there's more variables. Then you swapped pistons, right? So there's more variables right there. Did your do a pressure/vacuum test after roaching the piston? If not, how do you know that you didn't have an air leak that caused the meltdown but you fixed it with the rebuild?

 

[oosik]

I have two Stihls. One big - the other is small. The owners manuals for both says - 87 octane will less than 10% alcohol. I have a JD G100 riding mower - owners manual says 87 octane with less than 10% alcohol. That is EXACTLY what I've been running in all three pieces of equipment since I purchased them 15 years ago and have never had a moments problem related to fuel.

 

[Wagtail]

Meh....regular gas and a 50:1 ratio.

Agree. Besides that, the lowest non-ethanol octane petrol I can buy at the pump is 91. I've never had a problem with my 2-stroke engines or the 4-stroke B&S in the D110. And the ute gets a hellofva lot better "mileage" with it, over the E10 'green' ethanol* stuff.

(*Our ethanol is cane sugar derived, too)

 

[Wolfy]

I do now, but at the time I owned that saw I did not have the knowledge to do a pressure test. I took it to the dealer who recommended high octane. I ended up trading it for a Stihl MS361 which has been run on high octane its whole life. If you look in the owner's manual it says to use a minimum of 89 octane.

 

[doneill127]

I have a husqvarna backpack blower and the manual calls for minimum 89 octane or voids warranty. Says lower octane can cause detonation and damage piston. The manuals for both my echo trimmer and chainsaw also require minimum of 89 octane. All my 4 strokes with Briggs an Techumseh motors require 87 minimum

 

[marchanna]

It’s a design characteristic. Higher compression allows you to get more useful energy out of the fuel with a given displacement, but requires a higher octane. I have had one motorcycle that requires 87 and another 89. I’ve had some cars that require 91. Unless you’ve modified the compression ratio or added a turbo or blower, you should just follow what you manual indicates. If you tend to own several pieces of equipment, it’s always easier to use one grade of fuel for all, so it’s always good to inquire prior to purchasing.

People have all sorts of opinions on this matter and anecdotal experiences, but like always, it’s best to search the facts in order to make an informed decision.

 

[fried1765]

It’s a design characteristic. Higher compression allows you to get more useful energy out of the fuel with a given displacement, but requires a higher octane. I have had one motorcycle that requires 87 and another 89. I’ve had some cars that require 91. Unless you’ve modified the compression ratio or added a turbo or blower, you should just follow what you manual indicates. If you tend to own several pieces of equipment, it’s always easier to use one grade of fuel for all, so it’s always good to inquire prior to purchasing.

People have all sorts of opinions on this matter and anecdotal experiences, but like always, it’s best to search the facts in order to make an informed decision.

The good news for you in NS is that ALL your premium grade automotive gasoline has NO ethanol.
Same for PEI, and NB, I believe.

 

[MossRoad]

Several responses state that non ethanol gas is not available.
That is not quite factually correct.
You can buy non ethanol (100LL) at any airport, in any state, in the USA.
I use it in my 8N, my gas Ford 3400, and mowers, generators, and saws.
It also stores much better than regular automotive gas.
One thing though: It is NOT CHEAP.
Local fire departments use it in all their small engines, because automotive non ethanol is banned in my (liberal) state.

Which state is that?

 

[LD1]

As others said.....run no less than manual calls for. Higher won't hurt, but it don't help either.....other than helping lighten your wallet.

If the 357xp manual said 87 is fine....then that wasn't your problem. If the manual said to use 89 and you chose to ignore it and run 87.....then yea, octane could indeed be the cause....but who's fault would that be.

A dealer simply telling me to run high octane.....I wouldn't trust that dealer. They are clueless about what octane means.