Let's assume we have half a tank of 93 octane gas in our car. Then, let's say we fill up with 100 octane race gas. What is now the octane rating of our full tank of fuel?
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Octane equalization
- Thread starter KGP
- Start date
I am guessing here but I think they average since both parts are equal. So that would be 96-97. I think this is how it works from hanging around the dragstrip, but I have no proof to back it up just track mythology, but that has never been wrong yet. Ya Right. 
I do know you have about $50.00 in it. Ah, the price of going fast just keeps going up, The grin on your face, Priceless!
Dave
I do know you have about $50.00 in it. Ah, the price of going fast just keeps going up, The grin on your face, Priceless!
Dave
The Gasoline FAQ (see 6.15) agrees with Dave:
“In general the octane response will be linear for most hydrocarbon and oxygenated fuels e.g. 50:50 of 87 and 91 will give 89.”
Caveat:
“…attempts to blend in your fuel tank should be carefully planned. You should not allow the tank to become empty, and then add 50% of lower octane, followed by 50% of higher octane… You should refill when your tank is half full.”
“In general the octane response will be linear for most hydrocarbon and oxygenated fuels e.g. 50:50 of 87 and 91 will give 89.”
Caveat:
“…attempts to blend in your fuel tank should be carefully planned. You should not allow the tank to become empty, and then add 50% of lower octane, followed by 50% of higher octane… You should refill when your tank is half full.”
Ojas said:
Well that part is curious. Why would it matter? Unless they mean really empty which is generally a bad idea due to the risk of sucking crud out of the bottom.
I too would suspect that by blending they would simply average out. Reason I brought this up is that I was browsing through some old threads last night (FI forum ), and in one of them Mark Basch mentions that different octane mixes do not average out, and that he got that information from a petrol engineer but couldn't remember the specific reason or formula.
Thanks for the URL, Ojas.
), and in one of them Mark Basch mentions that different octane mixes do not average out, and that he got that information from a petrol engineer but couldn't remember the specific reason or formula.Thanks for the URL, Ojas.
Do fuels of different octane ratings have different weight characteristics? If thats the case it would be like trying to mix water and oil at a different level of course. Just a thought
Armando
Armando
My bad
“Yes, however attempts to blend in your fuel tank should be carefully planned. You should not allow the tank to become empty, and then add 50% of lower octane, followed by 50% of higher octane. The fuels may not completely mix immediately, especially if there is a density difference. You may get a slug of low octane that causes severe knock. You should refill when your tank is half full. In general the octane response will be linear for most hydrocarbon and oxygenated fuels e.g. 50:50 of 87 and 91 will give 89.”
It seems like the author is interested in blending different octane ratings to save money by mixing the engine’s recommended octane with a cheaper, lower one. In that case, I could see why that would be a bad idea and it would be better to fill with the recommended octane followed by the lower one. So, the warning would not apply to all cases of mixing octanes, only those where the average would be lower than recommended (to minimize knock).
We would be running a high-than-recommended octane, so the order may not make much of a difference, since we are not exposing the engine to risk of knock. However, it seems like filling with recommended followed by higher would be the way to go, since the first few gulps of gas would closer to what the engine's used to sipping.
You're right. Now that I think about it, that does not make much sense. I re-read the original paragraph and realized I probably got a little too ellipsis-happy when quoting, leaving out a couple relevant sentences (underlined below):sjs said:
“Yes, however attempts to blend in your fuel tank should be carefully planned. You should not allow the tank to become empty, and then add 50% of lower octane, followed by 50% of higher octane. The fuels may not completely mix immediately, especially if there is a density difference. You may get a slug of low octane that causes severe knock. You should refill when your tank is half full. In general the octane response will be linear for most hydrocarbon and oxygenated fuels e.g. 50:50 of 87 and 91 will give 89.”
It seems like the author is interested in blending different octane ratings to save money by mixing the engine’s recommended octane with a cheaper, lower one. In that case, I could see why that would be a bad idea and it would be better to fill with the recommended octane followed by the lower one. So, the warning would not apply to all cases of mixing octanes, only those where the average would be lower than recommended (to minimize knock).
We would be running a high-than-recommended octane, so the order may not make much of a difference, since we are not exposing the engine to risk of knock. However, it seems like filling with recommended followed by higher would be the way to go, since the first few gulps of gas would closer to what the engine's used to sipping.
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Certainly not "water and oil." Maybe more like salt water and fresh water I would think.MiamieNeSeX said:
Yippy I was right, thats two time already this year, That is better than last year.
Dave
Dave
They mix fine. Here is a link to the Union 76 web page that has the ratios. They also print this on the side of the 5 gallon cans of the 100 octane race fuel. So I get about a 94 accordbng to the chart. 10 Gallons of 91 and 5 gallons of 100. You guys that get 93 octane for premium have it made.
http://www.76.com/products/76racing.asp#OCTANE
When I mix it I use 5 gallons of race fuel and the rest crappy california 91 octane
I only run 76 fuel in my car cause they are the only ones that don't use methanol, I have had detonation problems running Chevron and others. Then I have to go find a 76 that sells racing gas to mix with the old crap to get the car to run right.
http://www.76.com/products/76racing.asp#OCTANE
When I mix it I use 5 gallons of race fuel and the rest crappy california 91 octane
I only run 76 fuel in my car cause they are the only ones that don't use methanol, I have had detonation problems running Chevron and others. Then I have to go find a 76 that sells racing gas to mix with the old crap to get the car to run right.
Some of the products don’t mix well.
Gas stations use (1) Research octane + (2) Motor octane divided by 2 for (3) Pump octane.
Research rating is a bogus theoretical rating that allows a range of error and that error is usually used to fool consumers. (Even some race fuels use this) You should ask!
Motor is a real world tested rating
Pump is an average of the two developed by our government to help the consumers from getting ripped off.
Octane is defined as; a rating for the speed that fuel burns at. Many different chemicals and elements are used to get higher octane ratings (Slower Burn). Lead is the best element for doing this, and unleaded fuels use other chemicals like propylene. I was in the fuel business for many years, and in this industry there is a running joke about the environmentalists that pushed for lead to be removed from our gasoline. The additives used to replace it are rated millions of times worse for our health and environment. (as tested in part per million of water) These chemicals are very expensive, as many of you know from buying race fuel… or even today’s pump gas.
Bottom line is- buy the octane that you need. And don’t spend the money if you don’t need more then pump. If you are going to mix, because you cant locally buy the octane you need for the money you want to spend, then only mix two similar fuels like 110 motor octane VP (leaded) with 116 motor octane VP (leaded) this will give you 113 motor like you would expect. (In fact this is what VP does) If you were to mix two products that were not compatible (Especially Unleaded) you may only dilute the higher number without adding to the lower. Unleaded additives don’t keep stacking for greater ratings.
No unleaded chemical has been found to raise the Motor octane above 108 and that costs about $40 a gallon. Yes, I know you can buy 110 unleaded, but your buying Research or lies. The normal 110 unleaded tests between 101 and 103 Motor octane. While backed with big sponsor money, we paid large amounts to win, and much of that money was to a fuel manufacturer to develop that $40 a gallon fuel. We also dyno'd every unleaded fuel anyone has ever heard of, Even some of the “top secret” fuels made in a garage for super cross pro’s. The next best, or commercially available Unleaded fuel that allowed us to make the most power without detonation (On the dyno) was Sunoco B42 (It might have been 52, I don’t remember the number they use). This isn’t the company I sold for.
Gas stations use (1) Research octane + (2) Motor octane divided by 2 for (3) Pump octane.
Research rating is a bogus theoretical rating that allows a range of error and that error is usually used to fool consumers. (Even some race fuels use this) You should ask!
Motor is a real world tested rating
Pump is an average of the two developed by our government to help the consumers from getting ripped off.
Octane is defined as; a rating for the speed that fuel burns at. Many different chemicals and elements are used to get higher octane ratings (Slower Burn). Lead is the best element for doing this, and unleaded fuels use other chemicals like propylene. I was in the fuel business for many years, and in this industry there is a running joke about the environmentalists that pushed for lead to be removed from our gasoline. The additives used to replace it are rated millions of times worse for our health and environment. (as tested in part per million of water) These chemicals are very expensive, as many of you know from buying race fuel… or even today’s pump gas.
Bottom line is- buy the octane that you need. And don’t spend the money if you don’t need more then pump. If you are going to mix, because you cant locally buy the octane you need for the money you want to spend, then only mix two similar fuels like 110 motor octane VP (leaded) with 116 motor octane VP (leaded) this will give you 113 motor like you would expect. (In fact this is what VP does) If you were to mix two products that were not compatible (Especially Unleaded) you may only dilute the higher number without adding to the lower. Unleaded additives don’t keep stacking for greater ratings.
No unleaded chemical has been found to raise the Motor octane above 108 and that costs about $40 a gallon. Yes, I know you can buy 110 unleaded, but your buying Research or lies. The normal 110 unleaded tests between 101 and 103 Motor octane. While backed with big sponsor money, we paid large amounts to win, and much of that money was to a fuel manufacturer to develop that $40 a gallon fuel. We also dyno'd every unleaded fuel anyone has ever heard of, Even some of the “top secret” fuels made in a garage for super cross pro’s. The next best, or commercially available Unleaded fuel that allowed us to make the most power without detonation (On the dyno) was Sunoco B42 (It might have been 52, I don’t remember the number they use). This isn’t the company I sold for.
Here's a friend of mine's homebrew octane guide http://www.theoldone.com/forum/topic.asp?TOPIC_ID=15110
There is always Toulene
A friend of mine brought several cans of Toulene to the track. That is about 100 octane right ?
A friend of mine brought several cans of Toulene to the track. That is about 100 octane right ?
sjs said:
I believe that it would matter because at the time of the filling the 50% tank would already be mixed well. When adding 25% of a high octane and 25% of a lower octane they would be mixing with a base that is already premixed. If you think about it this way it would be better to add extra fuel when the tank was 90% full, since this really isn't too feasible I would think that half full would work well. I would guess that the engine would get a nice mix through the next half tank of usage.
When adding 50% of a high ocatane and 50% of a low octane it would take some time before these two would be mixed well.
The engine would probably get a wide range of variance for the first few miles.
Close. Actually it is just a value used to indicate the resistance of a motor fuel to knock as measured on a test engine, relative to isooctane = 100 (minimal knock) and n-heptane = 0 (bad knock). Flame speed (ie. speed of combustion) is one factor, precombustion due to pressure is another.RacerX-21 said:
114.Fanman said:
Carguy! said:
My point is that if you start close to empty and fill to half a tank, then you are in the same condition as if you had pulled in with half a tank. Right?
But do you really think it really takes that long to mix? I find it hard to believe that the turbulence of pumping fuel into the tank plus a little go/stop/turn driving would fail to mix the fuel adequately. And unless you are topping off at the drag strip immediately before a launch, any fuel in the lines and filter will be purged before you need the added octane.
Maybe I'm off base hear but it sounds like a lot of worry about nothing.
Toulene?
A friend of mine brought several cans of Toulene to the track. That is about 100 octane right ?
I have heard some talk about Toulene, how does that work? Can you just add it to the tank and boost the octane? What is the down side and if it is that easy, why don't the gas suppliers do that?
A friend of mine brought several cans of Toulene to the track. That is about 100 octane right ?
I have heard some talk about Toulene, how does that work? Can you just add it to the tank and boost the octane? What is the down side and if it is that easy, why don't the gas suppliers do that?
Search the forums for toulene and you should find a thread on this with links to some decent explanations of it. The short answer is that yes, it does raise octane but there are limits to how much you can add and some drawbacks.
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