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What fuel do you guys run?

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I have the pcm 5.7 excalibur 343 engine. Do you guys run regular fuel with ethanol and then stabilize the fuel? Only ethanol free? Or dont stabilize with e10 fuel and just drive it and don’t care?

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The only fuel at my dock is ethanol free but when I fill up at a gas station with regular I don’t add stabil. I’ve heard some detonation on initial acceleration when I run regular fuel back to back for a few tanks. So 88 or 90 octane would fix that.

 

 

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I run ethanol free premium gas plus I add marine stabil to every tank.  I have done this in all my boats and off road vehicles and never had an issue.

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Lower octane creates more heat

 

Huh? Why would heat equate to more power? If that were the case why would autos have EGR systems, oil squirters for bottoms of pistons, and intercoolers for forced induction, among other items to keep temperatures down?

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Higher octane burns slower. I suppose it’s debatable, but engine builders that I have talked with over the years have said that if you don’t need the higher octane for added compression, your engine will actually make more HP with the lower octane.

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I certainly would agree that higher octane fuel does burn/ignite slower, but have never heard of the latter. The octane rating is actually an anti-knock index. If you were to put a higher octane rated gas into a engine that does not require it, it would have almost no effect because the timing has been set to the octane rating that is recommended. I will say that if you get too out of hand with your octane rating, like running race gas in your grocery getter mini-van, yes, you will be running a slower ET at the track. This is because there is not enough compression to compress the air and fuel enough for optimum power and burn. But running better dyno numbers on 87 vs 91 on a properly tuned motor for that grade of fuel....eh, I have my doubts. 

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Once ignited, 87 and 93 have about the same BTU's. The difference is, 87 takes less heat to ignite, then 93. 93 has a higher resictance to igniting on its own due to heat. This is how spark knock/pre-ignition is prevented. No performance advantage to higher octane in an engine that does not require it due to compression ratio. 

 

There is a slight performance advantage to pure gas/non-ethanol, as the the E10 has a lower BTU. The long term benefits of using non-ethanol in a higher octane then required, can be worth the extra cost. 

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Man someone school me on this.  I am a mile high, non ethanol gas is not easy to come by so how does this affect us guys at altitude?  My manual says 89 octane or more.  I always run 91, when I've tried running 87 I noticed knocking & poorer performance after a couple tanks.  Should I be adding stabalizer to every tank?  Are we splitting hairs on this issues or??

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Man someone school me on this.  I am a mile high, non ethanol gas is not easy to come by so how does this affect us guys at altitude?  My manual says 89 octane or more.  I always run 91, when I've tried running 87 I noticed knocking & poorer performance after a couple tanks.  Should I be adding stabalizer to every tank?  Are we splitting hairs on this issues or??

You are right to run the 89 or higher for the safety of the engine, but only run as high as the next grade above 89 when not available. No advantage to pass a 91 pump for a 94 pump for example.  

 

On newer boats, im not real worried about running E10 as the system as designed to tolerate it. The issue can come from long layups with moisture absorption and phase separation. 

 

ethanol stabil is not needed every tank IMO, but doe snot hurt. I do think its worth it from time to time and definitely a good dose prior to layup.

 

Each tank of 87 you mix with an existing tank of 91, lowers the octane and increases the volatility. This is why you hear the knock and notice the timing retard. Stick to the manufacturers octane suggestion. Too expensive of a gamble to rely on the knock sensor to do its thing. id rather have no knock and full timing curve, then retarded timing to stop knock.  

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I have always ran 87 or 89 in all my boats with no stabilizers and have never had any knocking or fuel issues. I don’t believe you need a stabilizer unless the boat will be sitting for close to a year, which mine does not. Mind you I’m at sea level but also run it at one lake that is about 5000’ so i’m Not sure what effect it would have at higher then 5000 foot elevation. Higher octane is for higher compression due to pre-detonation...def no performance advantage.

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Once ignited, 87 and 93 have about the same BTU's. The difference is, 87 takes less heat to ignite, then 93. 93 has a higher resictance to igniting on its own due to heat. This is how spark knock/pre-ignition is prevented. No performance advantage to higher octane in an engine that does not require it due to compression ratio. 

 

There is a slight performance advantage to pure gas/non-ethanol, as the the E10 has a lower BTU. The long term benefits of using non-ethanol in a higher octane then required, can be worth the extra cost. 

 

You are right to run the 89 or higher for the safety of the engine, but only run as high as the next grade above 89 when not available. No advantage to pass a 91 pump for a 94 pump for example.  

 

On newer boats, im not real worried about running E10 as the system as designed to tolerate it. The issue can come from long layups with moisture absorption and phase separation. 

 

ethanol stabil is not needed every tank IMO, but doe snot hurt. I do think its worth it from time to time and definitely a good dose prior to layup.

 

Each tank of 87 you mix with an existing tank of 91, lowers the octane and increases the volatility. This is why you hear the knock and notice the timing retard. Stick to the manufacturers octane suggestion. Too expensive of a gamble to rely on the knock sensor to do its thing. id rather have no knock and full timing curve, then retarded timing to stop knock.  

 

I went to a meeting and came back and looks like you covered it all pretty well, lol. You are pretty well versed in the audio and mechanical realm, well done. 

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Man someone school me on this.  I am a mile high, non ethanol gas is not easy to come by so how does this affect us guys at altitude?  My manual says 89 octane or more.  I always run 91, when I've tried running 87 I noticed knocking & poorer performance after a couple tanks.  Should I be adding stabalizer to every tank?  Are we splitting hairs on this issues or??

 

I am surprised that you have detonation issues at that elevation with 87 if the recommended is 89. The higher you go the thinner the air, and the thinner air makes up for the lack of octane. But there is no arguing the real world performance you are experiencing. 

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