?? 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.