Mixing octanes - do you know the formula?
Thread Starter
Race Director
Joined: Oct 2002
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From: Southern CA
Mixing octanes - do you know the formula?
It's high school math, I know, but I forgot, ok.
Let's say you mix 5 gal of 100 octane unleaded pump gas with 15 gal of 91 octane unleaded pump gas, what octane do you have in the tank?
or 2.5 gal 100 with 17.5 gal of 91, you get the drift?
TIA
Let's say you mix 5 gal of 100 octane unleaded pump gas with 15 gal of 91 octane unleaded pump gas, what octane do you have in the tank?
or 2.5 gal 100 with 17.5 gal of 91, you get the drift?
TIA
Burning Brakes
Joined: Feb 1999
Posts: 1,157
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From: Encino CA
I believe it is basically just the weighted average divided by the total number of gallons. So in your first example, 5 gallons times 100 plus 15 gallons times 91 equals 1865. Then 1865 divided by 20 gallons equals 93.25 octane. In the second example 2.5 gallons times 100 plus 17.5 gallons times 91 equals 1842.5. Then 1842.5 divided by 20 equals 92.125 octane.
Class dismissed.
Class dismissed.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
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From: backwoods upstate ny
i was manager of local gas station until a couple months ago...delivery manifests for mid-grade were often a mix of reg + super on the paperwork, just a linear relationship, as noted above
Race Director
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Years ago (don't ask me how many) it went something like this:
5 gal. of 89 octane + 5 gal of 91 octane = 10 gal of 92 octane.
That hasn't been the case in awhile, so if you don't believe it, it's understandable.
Larry
code5coupe
5 gal. of 89 octane + 5 gal of 91 octane = 10 gal of 92 octane.
That hasn't been the case in awhile, so if you don't believe it, it's understandable.
Larry
code5coupe
Thread Starter
Race Director
Joined: Oct 2002
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From: Southern CA
Huh?
Are you saying mix unleaded with leaded? Back in the day when I guess you could do that?
Then I would perhaps believe anything is possible.
Remember when you could carry a little "sizer" thing that fit in the small unleaded hole but let you pump from the big leaded nozzle?
Are you saying mix unleaded with leaded? Back in the day when I guess you could do that?
Then I would perhaps believe anything is possible.
Remember when you could carry a little "sizer" thing that fit in the small unleaded hole but let you pump from the big leaded nozzle?
Last edited by froggy47; Jul 12, 2006 at 08:29 PM.
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Team Owner
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From: Northern, VA
St. Jude Donor '15
"In honor of jpee"
It's true. Used to be a time when you could mix some lower octane gas with mid range and actually get a higher octane at the pumps. When it ended, I don't know. But, there was a time....
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by rocco16
Years ago (don't ask me how many) it went something like this:
5 gal. of 89 octane + 5 gal of 91 octane = 10 gal of 92 octane.
That hasn't been the case in awhile, so if you don't believe it, it's understandable.
Larry
code5coupe
5 gal. of 89 octane + 5 gal of 91 octane = 10 gal of 92 octane.
That hasn't been the case in awhile, so if you don't believe it, it's understandable.
Larry
code5coupe
ABSOLUTELY!!!Except as I remember it your answer of 92 is probably low. Back in the day, as low lead and unleaded gases were coming on line, the crappy no and low lead gases had to be much more highly refined than the leaded gases, just to have any octane at all. A mix of about 15 gallons of no lead with 5 gallons of premium could result in 15 gal of 87 + 5 gal of 92 = 20 gal of approx 98. It didn't take much of the lead from the leaded gas to drive the more highly refined, no lead gas, nuts.
RACE ON!!!
Safety Car
Joined: Sep 2002
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From: The reason time exists is so everything doesn't happen at once
Originally Posted by froggy47
Huh?
Remember when you could carry a little "sizer" thing that fit in the small unleaded hole but let you pump from the big leaded nozzle?
Remember when you could carry a little "sizer" thing that fit in the small unleaded hole but let you pump from the big leaded nozzle?
But I guess I'm just showing my age.
Team Owner
Joined: Jun 2005
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From: Northern, VA
St. Jude Donor '15
"In honor of jpee"
Originally Posted by CFI-EFI
ABSOLUTELY!!!Except as I remember it your answer of 92 is probably low. Back in the day, as low lead and unleaded gases were coming on line, the crappy no and low lead gases had to be much more highly refined than the leaded gases, just to have any octane at all. A mix of about 15 gallons of no lead with 5 gallons of premium could result in 15 gal of 87 + 5 gal of 92 = 20 gal of approx 98. It didn't take much of the lead from the leaded gas to drive the more highly refined, no lead gas, nuts.
RACE ON!!!