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6.0 on 87 Fuel


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I am considering the 6.0 for a new LSV, but I have heard these engines like premium fuel. Unfortunately I can only get 87 at my dock. I have heard with lesser grade fuel the engine has less power and is less efficient, thereby negating the point of getting a bigger motor than the 350.

What's the consensus on it?

I notice Indmar website specifies "Regular Unleaded"

http://www.indmar.com/Engine/malibu/Monsoon409SS.aspx

Edited by pkh
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I only run 91 in my boat, but that's just me, no matter what the grade. Can't you fill up on your way to the lake? I doubt much would happen. The Porsche turbo says use 93 octane or above, and we don't have that in ca, nothing bad after so many years.....

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Regular should be fine on that motor. The L96 iron block 6.0 is truck motor, which has an 87 octane requirement. You should have no issues with that. The L96 is the replacement for the LY6 - only real difference is being flex fuel compatible, which isn't used in boating applications.

You always want to run as little octane as possible WITHOUT KNOCK to get max performance. Once knock is seen by the ECM, it will pull timing and take power where you want it most - down low and wide open and end up being less efficient. But if the motor is designed for 87, no problems.

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Nitrous is spot on. Octane does nothing for power, it just increases the flash point. If anything it might actually decrease BTU's. If the 6.0 was designed for 87 then go with it. I think it is more important to look for gas without ethanol. One last suggestion, consider the 6.2 if you are going to do an engine upgrade.

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Nitrous and Tims are spot on. Running a higher octane will do nothing but empty your pocket book faster. Higher octane gasoline say 91 vs 87 has not more BTU...the higher octane only delays/retards the flash point (when the gas in the compressed cylinder goes kabooom)...that is why higher octane is always recommended in higher compression vehicles. Higher octane gas won't get you better gas mileage, won't make your engine last longer, etc....only empty your pocket book faster.

Ethanol has approx 85% of the BTU value that gas has. Diesel, surprising has the most BTUs at about 135,000, gas is about 100,000.

I run 87 in my LS3, and has never knocked....and she gets the best of everything.

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I have 150hrs on my 6.0L.... majority is heavy loads wakesurfing.

The only reason to run higher octane gas is to prevent knocking...i have used everything from the Pilot Truck stop 87 cheapie gas, to Shell 91, to the ethanol free. My engine has NEVER knocked or shown any difference in performance betwen any of them.

I DO try to run the ethanol free gas whenever possible. Also, I always run the Stabil Marine ethanol treatment stuff all the time.

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PKH,

The fuels octane number is more about the temperature required to ignite it, and not about its power or fuel economy. Once ignited, 87 oct has about the same BTU's at 93. 87 oct is more volatile and ignites at a lower temp them 93 oct. This is why higher octane is recommend for higher compression engines. Higher compression equals higher combustion chamber temps.

Running lower octane fuel in a higher compression engine can lead to reduced performance, but its not directly related to the fuel. If the lower octane fuel causes pre-ignition, this leads to reduced power and also the ECM will sense the knock and retard the timing. In an engine designed for 87, there is no performance advantage to running higher octane fuel. For engines with higher compression, where higher octane fuel is recommended, there can be a performance advantage to running the higher octane fuel. Pre-ignition will also damage an engine if it is prolonged. Run ewhat the engine manufacturer recomends, or higher if thats not available.

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The guy here who used to do all the small engine repair (mowers, blowers, edgers, etc) here in town, and who pulled them apart for a living swears that for small engines premium fuel will save you tons on repair bills and make them last way longer. Since there are obviously a few people here who know about engines, does that make any sense? Sorry for the mini hijack.

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The only other thing worth mentioning is that octane will drop if the fuel sits around for a long time. If your boat spends a fair amount of time in storage between outings, the higher octane will stay in the 87 to 91 range longer than 87 octane gas will.

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I run 87 in my LS3, and has never knocked....and she gets the best of everything.

You are not going to hear it knock, as the ECM will pull timing from the motor. You are likely burning MORE fuel than if you would run 93...you might actually be losing money running 87. The LS3 is a 10.7:1 motor...that's a bit high for 87 octane. I bet just going to 89 will net you better fuel mileage and performance.

Most car ECM's (and I assume boat as well) have fuel and timing tables for low ocatane fuel. Basically if the knock count gets high enough on the knock sensor, the ECM will simply go to the low octane table (some other factors have to be met as well, but generally speaking).

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The same rules on fuel apply to the 6.2 and S/C 550. If Indmar says they can run on 87 then they will be fine with that grade of gas. Compression ratio plays a factor, but the real issue is heat and combustion chamber design. GM is coming out with a new LS motor next year that will finally go with direct injection, allowing for higher compression ratios with less heat. That will be a big boost to torque and efficiency.

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This is from the 2012 Indmar manual:

Capture2.jpg

I was reading this thread thinking I had lost my mind. I knew that is what my owner's manual said. I don't always do it, for the reasons stated above, but nonetheless, I was told by the owner's manual to use 89 octane. It always makes me a little nervous to go away from what an owner's manual says, but I see these sorts of threads for years, and the gear heads that really know their stuff seem to echo the idea that higher octane is only good for emptying out your wallet.

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I was reading this thread thinking I had lost my mind. I knew that is what my owner's manual said. I don't always do it, for the reasons stated above, but nonetheless, I was told by the owner's manual to use 89 octane. It always makes me a little nervous to go away from what an owner's manual says, but I see these sorts of threads for years, and the gear heads that really know their stuff seem to echo the idea that higher octane is only good for emptying out your wallet.

Check out Indmar's website. They for all boats (Supra, Moomba, their straight Indmar line, Axis, and Malibu) that the GEN-I SBC's and L96 motors are regular. They flip-flop between regular and premium depending on what brand is selling the LS3 and LSA.

The old GEN-I's have been known to run on regular. L96 is a truck motor, so regular should be okay. LS3 is from the '08-'13 Vettes and '10+ 6-speed Camaro's, both which call for premium. The LSA, from the '09+ CTS-V and '12+ ZL1 Camaro, also require premium.

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I would be confident running 87 gas in the LS3 as long as it did not have any ethanol. Computer will compensate for any "pinging/knocking". I would be much more nervous about damage with the supercharged engine since the higher combustion pressures could potentially cause a "pre-ignition" condition which is deadly for the engine. Pre-ignition is when you have uncontrolled ignition before spark. This causes extremely high heat in the cc and will quickly destroy a motor. Detonation or "pinging" is caused after spark ignition which causes high cc pressures and a sound wave which produces the knock sound. This can be controlled by retarding the ignition (knock sensors). The difference between 87 and 89 is silly from the engines point of view but the oil companies love the margin they get when you buy it.

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Check out Indmar's website. They for all boats (Supra, Moomba, their straight Indmar line, Axis, and Malibu) that the GEN-I SBC's and L96 motors are regular. They flip-flop between regular and premium depending on what brand is selling the LS3 and LSA.

The old GEN-I's have been known to run on regular. L96 is a truck motor, so regular should be okay. LS3 is from the '08-'13 Vettes and '10+ 6-speed Camaro's, both which call for premium. The LSA, from the '09+ CTS-V and '12+ ZL1 Camaro, also require premium.

Is premium 87, 91 or both?

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That's how it is here too, though premium can be 92 or 93...or 94 back when Sunoco sold their good gas. 91 only seems to be common in the People's Republic of Kalifornia.

Thats cause everything is sooo different out here...ya know even the air is different in CA...maybe that is why the cows are so happy??...so we have to have our special seasonal blends...which adds to the cost of our special gas. Ya gotta love it.

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Doesn't ethanol actually increase the octane rating? I have a few buddies that have high compression quads that run E85 because it is around 105 octane. Granted they burn more fuel now because they had to increase the jet sizes. And the exhaust smells funny! I get that the BTU is actually lower, but wouldn't that help the detonation issue? I don't like running it in anything, because it gums up and is hard on the fuel system. But, not many places around here have fuel without it.

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