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I use regular, 87 octane as that is what is specified in the manuals. I also pour <an ounce of Marvels Mistery Oil in every fillup for more top end lubrication.
Spock
 

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85 for me we are at 4700 feet asl.
 
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What gas octane are you running? High Test? Mid Grade? or 87 octane / plain old regular?

Thanks
Joe


The engine is designed for 87 octane and there isn't any real reason to run a higher grade. Octane rating only addresses potential pre-detonation (engine knock) and not performance so why run a higher grade?


With that said I actually run 89 octane to provide slightly more pre-detonation protection because pre-detonation causes severe harm to an engine. There are a lot of steep grades where I live and pre-detonation occurs when the engine is under heavy load like when climbing a steep grade. "An ounce of (extra) prevention" only costs me a few cents per fill-up. Admittedly I'm probably stupid to be using a higher octane rating gasoline.
 

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I use regular, 87 octane as that is what is specified in the manuals. I also pour <an ounce of Marvels Mistery Oil in every fillup for more top end lubrication.
Spock


Some people swear by Marvel Mystery Oil and I used it when I owned my 1928 Oldsmobile but I don't believe it's necessary for modern engines. There really isn't anything to lubricate (i.e. the valve guides are lubricated from the engine oil).


My biggest concern would be that it might result in clogged fuel injector ports over time as it's denser than gasoline and could build up in the port. I don't know of that actually happening but do know that using a fuel injector cleaner once in awhile is a good idea.


But some people love it and if they want to use it then it's their engine and they are certainly welcome to do so.
 

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It's like how some people swear by using sea foam, but it's not all that necessary. Using it on an older engine might help a bit and make you feel better about it in the process.
 

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Modern engines, as already stated earlier by other members do not require additional lubrication. By adding oil to the fuel will only lead to clogged injectors, sticky valves, extra deposition of carbon on the cylinder head and even carbon and maybe sludge in the exhausts. All this is just not desirable. Best to run the machine as it is designed to be run. As they say, "Follow the Doctors orders".:)
 

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My Stealership told me to use 93 octane only.... Maybe next fill up I will through 87 in there ti see if I get an "pings"
 

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My Stealership told me to use 93 octane only.... Maybe next fill up I will through 87 in there ti see if I get an "pings"

For a street the dealership said 93?

Owners manual and service manual both indicated 87. And that is at sea level.
 
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For a street the dealership said 93?

Owners manual and service manual both indicated 87. And that is at sea level.

With EFI and electronic ignitions I don't believe elevation is a consideration (except for lower performance due to lower atmospheric pressure). Modern engines with electronic ignitions and EFI are designed to change the timing slightly with elevation changes to eliminate pre-detonation. I'm not sure that this is programmed into the Street Harley's but it probably is. I've never had a problem with my Sportster at elevations and it is a simple programming requirement for the engine that doesn't cost the manufacturer anything.
 

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Elevation allows you to use a lower octane fuel since the compression of the engine is less at elevation.

Definitely a performance effect.

EFI corrects the AF ratio for a clean burn and proper temperatures, it can also stop some predetonation by altering the injection point, but most pre-detonation is a compression factor. Further apart the atoms that make the air up expand with elevation increase, the less O2 sucked into the fixed volume cylinder of any naturally aspirated engine. The lower the pressure in the cylinder on the compression stroke.
 
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My dealership told me the same thing. High octain. But the book says 87. Ive been running high test. Maybe ill try 87 and see if it makes any difference
 

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My dealership told me the same thing. High octain. But the book says 87. Ive been running high test. Maybe ill try 87 and see if it makes any difference


The factory is almost always correct and it does provide the minimum octane rating that should be used. The problem I find is with those that think a higher octane has more energy improving performance and that is a false belief. The octane rating has nothing to do with the amount of horsepower produced by the engine. Higher octane will not hurt an engine but it won't increase HP either.
 

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The factory is almost always correct and it does provide the minimum octane rating that should be used. The problem I find is with those that think a higher octane has more energy improving performance and that is a false belief. The octane rating has nothing to do with the amount of horsepower produced by the engine. Higher octane will not hurt an engine but it won't increase HP either.
This is so true i have seen many articles and information that show how useless going with higher octane is when it's not required. Best to go with what is recommended for it.
 

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This is so true i have seen many articles and information that show how useless going with higher octane is when it's not required. Best to go with what is recommended for it.


Or be stupid like me and us 89 octane when I know it only needs 87 octane. LOL
 

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Or be stupid like me and us 89 octane when I know it only needs 87 octane. LOL

You are prepared to ride below sea level in Death Valley with no preignition problems.
 
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You are prepared to ride below sea level in Death Valley with no preignition problems.


hmmmmm.... October and the daytime temperatures are becoming bearable in Death Valley and I haven't been to Stovepipe Wells in over 30 years.... stop giving me ideas. LOL
 
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hmmmmm.... October and the daytime temperatures are becoming bearable in Death Valley and I haven't been to Stovepipe Wells in over 30 years.... stop giving me ideas. LOL
Oh ya I am twisting your arm.......

Hah once you have the disease there is no cure....>:D>:D>:D
 
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Oh ya I am twisting your arm.......

Hah once you have the disease there is no cure....>:D>:D>:D


I checked the weather forecast for Death Valley and it's going to be 94F today. Still too hot for me. LOL
 
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