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Discussion Starter #1
I asked some folks I know about blend-at-the-pump gasolines. RandyO mentioned that there was a time when one company offered numerous octane blends by blending at the pump. After rolling on the floor laughing for a while, the chemists said that, yes, they remembered that and, yes, it's possible to do it, but practically speaking it doesn't work. The explanation was a bit above my head, but the concensus was that you could probably blend regular and premium, and if you really watched the hydrocarbon population of both grades, come reasonably close to an intermediate octane. There were numerous factors that would affect the success of the procedure. It would be harder to do it right in hot weather because of lighter hydrocarbon flashing (the gasoline in the storage tanks changes slightly if it sits there a while because the lighter ends evaporate). The gas you actually pump into your tank may or may not be the advertised octane depending on how fresh it is, hence the recommendation to buy gas where the station sells a lot of it. There were a lot of other caveats about the procedure, but in a nutshell that's it.
 

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Anyone really worried about the octane they are getting from the pump, can just throw some toluene in their tanks at each fill up. ;)
 

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Listen...my best friend owns a gas station. He just put new pumps in. The new pumps mix fuel. I dont know the chemistry behind it but just about any pump that has 1 nozel mixes fuels. His old pumps had three nozzles. Just think of this. If you pull up to a pump with 1 nozzle and you want premium...but the guy before bought regular...you are getting about .5-1 gallon of regular that was in the line after the switching point! Octane isn't that specific. The state comes by and tests all his pumps for all grades at least twice a year. If mixing fuel was that inaccurate dont you think someone would have figured that out?
 

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i think i'm going to convert my sv to run of used french fry grease. that solves the problem.
 

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B.a. said:
i think i'm going to convert my sv to run of used french fry grease. that solves the problem.
Let us know how that work's out for ya. :)
 

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avc8130 said:
Listen...my best friend owns a gas station.  He just put new pumps in.  The new pumps mix fuel.  I dont know the chemistry behind it but just about any pump that has 1 nozel mixes fuels.  His old pumps had three nozzles.  Just think of this.  If you pull up to a pump with 1 nozzle and you want premium...but the guy before bought regular...you are getting about .5-1 gallon of regular that was in the line after the switching point!  Octane isn't that specific.  The state comes by and tests all his pumps for all grades at least twice a year.  If mixing fuel was that inaccurate dont you think someone would have figured that out?
I don't think that pump is mixing the fuels, instead it's swtitching from one source to the other as needed. It only pumps from once source at a time.
 

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zoltan said:
I don't think that pump is mixing the fuels, instead it's swtitching from one source to the other as needed. It only pumps from once source at a time.
Correct.

If you have ever looked inside one of the pumps, you can see a manifold with all the different grades of gas are being pumped in, and then out the one nozzle.

Its just not cost effectivte to have a nozzel for each grade.
 

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Ok, so I just talked to my buddy who owns the shop.  What he said was that there are two hoses: one for regular and one for premium.  The pump mixes right there.  Also, whatever gas isnt dispensed drains from the line so if the guy before you gets premium, you wont get any when you get regular.  
He used to have 3 nozzle pumps.  Then he had three tanks and nothing mixed.  When he went with the single nozzle pumps he had to bridge 2 tanks together to hold regular and it mixes in premium from the 3rd tank to make midgrade at the pump.
He also confirmed that midgrade was just something someone in marketing devised to get extra $$ out of the consumer.  I have never seen a car designed that required 89 over 87 or would require 89 instead of 91.  It just plays off the fact that people think higher octane is "better" gas.
 
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avc8130 said:
"...He also confirmed that midgrade was just something someone in marketing devised to get extra $$ out of the consumer..."
Learn something new everyday!

Just thinking about it, I don't recall there being a midgrade when I started driving: there was regular, super and unleaded. Cars then were far more sensitive to octane than they are now, what with knock sensors and FI.

:)
 

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so, Andy, are you telling us that if we bought some oddball Sunoco octane grade, we weren't getting what we were paying for, or an approximation at best
 

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Discussion Starter #11
Pretty much. That's a fact of life with any gasoline. It is true that the fuels are tested, but there is an acceptable range of error. The notion that you can blend tankage gas and hit one octane number on the nose is dubious at best. It's not likely that all the 87 you buy is exactly 87 either. The current regular-to-premium step is realistic, about 6 differential.

And gas is less likely to match its advertised octane in the summer at stations that have low sales.

The short story is that stock SVs seem to run fine on regular and that's what should be in the tank. Modified bikes are a different story. Run the lowest octane that doesn't ping.

I asked about the hose drain, and there is no way for the hose itself to purge, at least at Shell or BP stations. If there is a single hose you can expect about a quart of whatever the last guy pumped.
 

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You never get the exact octane that you think you are.  You're probably getting a little bit higher octane.  Read the fine print on the pumps.  It says minimum octane rating87.

That's if you can even believe anything that you read.
 

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Actually hose drain isnt an issue. When you let go of the trigger the gas that is in the line drains out. The part after the pump drains back down and the part in the line after the loop at the top drains throught the nozzle. You really are getting what you paid for...to the tested standards assuming tolerances of course.
ac
 

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This debate should end, its going nowhere fast. LOL
 

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Discussion Starter #15
At this point it's not a debate, it's a dispute about facts. The people I asked said that there is no way for the gas to drain back. There are check valves in all the lines, there is no return from the nozzle, it's all one-way flow.

They pointed out that if the hose were drained then you would get vapors, not liquids, until the vapor space in the hose exhausted out the nozzle. There is another good reason to keep the hose liquid-filled. The vapor space would inevitably have air in it, which could result in an explosive mixture in the hose. My experience tells me there's nothing but liquids in the hose.

Now, how much an effect all this has on the octane in a tankful of gas is probably zippo. In all my years I've never felt any difference tank to tank, cars or bikes.
 

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yeah, but my point is, its a "he said/ she said" kinda of thing and no one is going to come out a winner, so why bother???
 
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A winner isn't required...there's a couple of members with good info to share, and you get to decide what you choose to believe. It's been an enlightening (and civil!) discussion.

:)
 

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While I understand what you are saying this is what I was told from my buddy who just got the brand new pumps. The guy who sold them (worked for the manufacturer) stated that two lines enter the pump at a manifold. If premium is drawn it comes from side A, regular side B. Then Midgrade is drawn 60% from A(premium) and 40% from B(regular). When the nozzle trigger is released the pump stops. The hose is routed up to the top of the pump. Then the trigger is released all gas below the top of the hose drains. The gas closer to the nozzle drains out the nozzle and the gas closer to the pump drains back down to the pump. If this is incorrect, I guess the manufacturer knows nothing about his product. Basically he said customers would be getting 100% what they paid for.
ac
 

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nc_sv650 said:
A winner isn't required...there's a couple of members with good info to share, and you get to decide what you choose to believe. It's been an enlightening (and civil!) discussion.

:)
OK, carry on then. LOL
 
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