What fuel octane should I run?

Sprky

Petty Officer 1st Class
Joined
Aug 7, 2011
Messages
277
Re: What fuel octane should I run?

87 is plenty
 

Bill3434

Petty Officer 1st Class
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May 29, 2011
Messages
398
Re: What fuel octane should I run?

If it is running rough you might try 89 octane. My old 70 doesn't like 87, my boat mechanic said I can try 89 and see what it does; runs much better. I asked about using 91 and he looked at me with a crazy look and said don't do it.
 

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: What fuel octane should I run?

It's a waste of money in all but racing outboards to use anything more than 87 octane. Higher octane fuel produce no more power, costs more and results in more deposit formation than 87. But hey, it's your money.
 

5150abf

Vice Admiral
Joined
Aug 12, 2007
Messages
5,808
Re: What fuel octane should I run?

Octane is one of the most misunderstood things on the planet, everyone thinks because high performance cars use high ocatane it must be better gas and give more power, can't tell you how many times I have seen Junior at the racing gas pump with moms Buick thinking that it is going to magically make the car more powerful.

The higher the octane rating the slower the gas burns which is why high octane is used in racing engines, the high compression causes detonation so those engines need a fuel that burns slower.

Old 2 strokes are low compression engines and don't need anything more than regular unleaded.

Now the more expensive fuels have additional addatives that may clean out the engine and make it run better because there is less carbon or the jets are cleaner but it has nothing to do with the gas itself.


87 burns more readily than 91 so your engine should run better on the lower octane since it is easier to ignite.
 

guitman32

Petty Officer 2nd Class
Joined
Aug 14, 2010
Messages
114
Re: What fuel octane should I run?

The manual for my '89 175 calls for 91 octane.

Aside from the manual, I use it for the benefit of detonation resistance. Not for any performance benefit (as has been stated).
 

Bill3434

Petty Officer 1st Class
Joined
May 29, 2011
Messages
398
Re: What fuel octane should I run?

It's a waste of money in all but racing outboards to use anything more than 87 octane. Higher octane fuel produce no more power, costs more and results in more deposit formation than 87. But hey, it's your money.

Never had a problem with more deposit formations with any of my engines where higher grade is used. Definately a waste of money if an engine runs fine on 87 though.
 
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