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Discussion Starter #1 (Edited)
Just out of conversation sake, I would like to find out what y'all thoughts were. I know the HD owners manual suggests 91 octane minimum and is what I have been doing for years in my HDs. But is it really any better, or worth the cost? I came across this video and have to say, I have my doubts. And how much 91 octane are we really pumping into our small tanks after someone pumped 87? Chances are, in my way of thinking, very little as the fuel travels a long way through hoses to get from the pump to my tank...:nerd:

https://www.youtube.com/watch?v=FPPkPAbzwbU
 

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I just filled up with 93 octane ethanol free yesterday @ 3.89/gal. It was either that or 87.

Normally, in a water cooled engine you can get away with whatever octane will keep you from detonating. If your CR isn't too high or timing to far advanced, that usually means 87 is fine. With an air cooled engine, that doesn't necessarily hold true, as detonation is also a product of cylinder head temperature. In the winter I can usually get away with running 89. When it gets hot out, I always run 92 or better , if possible, especially if I know I am going to be doing much stop and go where the bike won't be moving a lot.
 

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If your compression is below around 10:1 you could probably get away with a mid grade but for higher compression I wouldn't use anything less than Premium. The octane rating is just how well it resist detonation. The higher the number the higher the resistance. If your bike has been tuned by a certified tuner I would consult them.


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Discussion Starter #8
How much of that higher octane fuel are you actually pumping into the tank though after someone filled the lines with god knows what. Probably lowest octane...I am curious to find out. Always wondered that. Even so, I still pump in the higher octanes in the bike. But pump the cheapest petro in my cage. :grin:
 

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I used 89 last summer to experiment. I'm about at sea level and running stock compression. It ran just fine and didn't notice any detention. The bike seemed to run hotter though. After about a month I switched back to 93.
 

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According to the WSJ article below, there is only about 1/3 gallon of previous fuel remaining in the average pump. On average, I put about 5 gallons in when I fill my tank.

Assuming 5 gallons of 93 octane being pumped in and 1/3 of a tank of 87 gas left in the pump, the octane of the fuel added is about 92.6. Well above the requirement.

Science doesn't lie, your mechanic does.

Done.

http://www.wsj.com/articles/SB122944043385810527


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Discussion Starter #11
According to the WSJ article below, there is only about 1/3 gallon of previous fuel remaining in the average pump. On average, I put about 5 gallons in when I fill my tank.

Assuming 5 gallons of 93 octane being pumped in and 1/3 of a tank of 87 gas left in the pump, the octane of the fuel added is about 92.6. Well above the requirement.

Science doesn't lie, your mechanic does.

Done.

Does Fuel Get Left in the Gas Pump Hose? - WSJ


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Ah ha! That helps ease my mind a bit. lol Thanks for the info.
 

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According to the WSJ article below, there is only about 1/3 gallon of previous fuel remaining in the average pump. On average, I put about 5 gallons in when I fill my tank.

Assuming 5 gallons of 93 octane being pumped in and 1/3 of a tank of 87 gas left in the pump, the octane of the fuel added is about 92.6. Well above the requirement.

Science doesn't lie, your mechanic does.

Done.

Does Fuel Get Left in the Gas Pump Hose? - WSJ


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Far be it from me to not believe everything I hear from main stream media, but I don't believe it. The only fuel that would be left would be from the switching valve to the pump, and that would be miniscule, maybe a few ounces. There is almost nothing from the pump to the filler valve. Next time you do a fill up, put the nozzle in your tank and open the valve before you turn the pump on, see how much fuel you get.

IIRC, the switching valve is after the filters in the housing, so there would only be a few feet of line going to the pump, which I doubt is any bigger than 3/4". Most all pumps these days have vapor recovery systems which requires the use of a coaxial hose, so that big 1" hose you see isn't all full of gas, it has a second passage in it for return vapors. I'm pretty sure that all the single hose systems would be under the EPA purview. It isn't even a question on pumps with multiple pump/hose systems.

I get my gas at a little local spot near my house. Their pumps look a bit late 60's vintage, but the only have one style of fuel per pump. Good for me that one of them is non-E93.

 

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Far be it from me to not believe everything I hear from main stream media, but I don't believe it. The only fuel that would be left would be from the switching valve to the pump, and that would be miniscule, maybe a few ounces. There is almost nothing from the pump to the filler valve. Next time you do a fill up, put the nozzle in your tank and open the valve before you turn the pump on, see how much fuel you get.



IIRC, the switching valve is after the filters in the housing, so there would only be a few feet of line going to the pump, which I doubt is any bigger than 3/4". Most all pumps these days have vapor recovery systems which requires the use of a coaxial hose, so that big 1" hose you see isn't all full of gas, it has a second passage in it for return vapors. I'm pretty sure that all the single hose systems would be under the EPA purview. It isn't even a question on pumps with multiple pump/hose systems.



I get my gas at a little local spot near my house. Their pumps look a bit late 60's vintage, but the only have one style of fuel per pump. Good for me that one of them is non-E93.




Great "all media but the one I watch is a lie" monologue. And I'm sure your experiment was more in depth than the WSJ. Sorry. Couldn't resist.

Anyway, in mpholland's world, the operator would fill up with a concentration even higher than the 92.6 octane I initially calculated so it matters EVEN less if someone before you used 87.

In fact, about 92.971875 octane by my calculation using the same 5 gallons.


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I know that the drivers sometimes mix up the fuels that go into a particular tank, not always, but it has happened. Also the loading racks where the trucks get their fuel, also make some mistakes, once again, not often but it happenes. Higher Octane does nothing but protect from detonation, hence, the higher the performance/comp ratio, the more important it is to run high octane fuel. Normal cars such as the one shown, need nothing but the lowest grade fuel, as they are the lowest performance you can get, in order to get better mileage.
 

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Great "all media but the one I watch is a lie" monologue. And I'm sure your experiment was more in depth than the WSJ. Sorry. Couldn't resist.

Anyway, in mpholland's world, the operator would fill up with a concentration even higher than the 92.6 octane I initially calculated so it matters EVEN less if someone before you used 87.

In fact, about 92.971875 octane by my calculation using the same 5 gallons.


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I wasn't disagreeing with your conclusions, just the WSJ. I have seen that same article used in the same discussion on other sites. My "experiment" was working at multiple gas stations when I was younger, hence the IIRC's in my post, as it was over 30 years ago. Yes, that is probably more in depth than the WSJ. I am pretty sure their figure was calculated from a 1" hose at 8' long. .5²xπx96=75.4 in³=.33gal., and I disagree with its logic, or lack thereof. As for the "all media but the one I watch" monologue, again, flawed logic. I don't believe any of them.
 

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I wasn't disagreeing with your conclusions, just the WSJ. I have seen that same article used in the same discussion on other sites. My "experiment" was working at multiple gas stations when I was younger, hence the IIRC's in my post, as it was over 30 years ago. Yes, that is probably more in depth than the WSJ. I am pretty sure their figure was calculated from a 1" hose at 8' long. .5²xπx96=75.4 in³=.33gal., and I disagree with its logic, or lack thereof. As for the "all media but the one I watch" monologue, again, flawed logic. I don't believe any of them.

Just busting your balls.


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