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Gas Octane?


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#1 alsjunk OFFLINE  

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Posted January 05, 2013 - 12:19 PM

Is there any benefit in using higher octane gas in 70's era engines such as onan bf twins and kohler k series? Just wondering. 



#2 HDWildBill OFFLINE  

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Posted January 05, 2013 - 12:38 PM

As long as the engine isn't knocking I don't see any reason to put the higher octane in there.  



#3 jd.rasentrac OFFLINE  

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Posted January 05, 2013 - 12:39 PM

maybe this article in wikipedia will explain, especially 4 Effects of octane rating


Edited by jd.rasentrac, January 05, 2013 - 12:39 PM.


#4 jd.rasentrac OFFLINE  

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Posted January 05, 2013 - 12:42 PM

As long as the engine isn't knocking I don't see any reason to put the higher octane in there.  

Hi Bill, I think one reason could be a higher efficiency factor


Edited by jd.rasentrac, January 05, 2013 - 12:43 PM.


#5 HDWildBill OFFLINE  

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Posted January 05, 2013 - 12:59 PM

Hi Bill, I think one reason could be a higher efficiency factor

 

Would you really get that much of an efficiency factor compared to the higher cost in a small engine?



#6 boyscout862 ONLINE  

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Posted January 05, 2013 - 01:26 PM

If you are having problems with regular gas in most of these old engines it often means that your valve or ignition timing is off. That needs to be fixed or you wont get any efficiency. The older engines were designed for leaded gas which helped lubricate the exhaust valves. I have been using Marvel Mystery Oil in my gas for all engines to lubricate and clean the fuel and cylinders. Some of the engines show a noticeable difference in their running if I forget the Marvel.



#7 John@Reliable OFFLINE  

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Posted January 05, 2013 - 01:41 PM

If you are having problems with regular gas in most of these old engines it often means that your valve or ignition timing is off. That needs to be fixed or you wont get any efficiency. The older engines were designed for leaded gas which helped lubricate the exhaust valves. I have been using Marvel Mystery Oil in my gas for all engines to lubricate and clean the fuel and cylinders. Some of the engines show a noticeable difference in their running if I forget the Marvel.

Ditto, old engine's around here always get treated, especially with this ethanol crap they call gas.


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#8 HowardsMF155 ONLINE  

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Posted January 05, 2013 - 02:11 PM

My two cents:

Octane ratings have more to do with whether an engine knocks under load.  The main issues that cause knock are excessive compression, early spark, and incorrect fuel octane.  Carbon build-up can cause increased compression ratios, leading to knock.  Early spark due to incorrectly adjusted ignition can also cause knock.  Those factors should be corrected first before changing fuel octane.

Now, I HAVE seen reports that higher octane fuels don't have ethanol added to them, but I don't know if that is true.  I've also seen threads from people using aviation gas in their small engines, again more due to lack of ethanol than for any other reason.

One thing I have heard that actually makes sense is that the octane rating measures how fast the fuel burns, and the higher the number, the slower the burn.  That means that high octane fuel in an engine that is not designed to use it actually wastes power, since it burns more slowly.


Edited by HowardsMF155, January 05, 2013 - 05:53 PM.

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#9 jd.rasentrac OFFLINE  

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Posted January 05, 2013 - 02:53 PM

Would you really get that much of an efficiency factor compared to the higher cost in a small engine?

Hi Bill, I only made a technical viewing. And btw, in germany you'll find only one sort of gasoline. We only have two different octane rates since 2 or 3 years (and most of the people use 95 octane) and therefore no savings capacities.

 

 

 

(And most engines today are diesel engines)


Edited by jd.rasentrac, January 05, 2013 - 03:06 PM.

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#10 jd.rasentrac OFFLINE  

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Posted January 05, 2013 - 03:08 PM

Is there any benefit in using higher octane gas in 70's era engines such as onan bf twins and kohler k series? Just wondering. 

The optimal octane rate you can find in the OM of your engine.



#11 JDBrian OFFLINE  

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Posted January 05, 2013 - 05:34 PM

I've started using high octane gas in my small engines but not for the octane. Locally the low and mid grade gas has up to 10% ethanol in it. This can lead to problems in fuel systems where it sits for long periods. The high octane does not have the ethanol in it. I'm not sure if this is true where you live. It's written right on the gas pumps at my favourite station. 



#12 A.C.T. OFFLINE  

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Posted January 05, 2013 - 06:13 PM

I've started using high octane gas in my small engines but not for the octane. Locally the low and mid grade gas has up to 10% ethanol in it. This can lead to problems in fuel systems where it sits for long periods. The high octane does not have the ethanol in it. I'm not sure if this is true where you live. It's written right on the gas pumps at my favourite station. 

This is what I use for the same reason. It is labeled for classic cars and small engines.



#13 IamSherwood OFFLINE  

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Posted January 05, 2013 - 06:19 PM

Same situation here, as with Brian. Low and mid grade have ethanol.

So I run high grade to avoid it.



#14 John@Reliable OFFLINE  

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Posted January 06, 2013 - 11:29 AM

Below is a website that lists gas stations who sell real gas.

pure-gas.org






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