premium gas

rolmops

rolmops

Vice Admiral
Joined
Feb 24, 2002
Messages
5,340
Re: premium gas

This is getting me mixed up.<br />Please bear with me.Am I right thinking that 87 octane means that the fuel is cracked down to 8 unit long hydro carbon chain molecules,with 87% of the fuel being at this unit length,whereas 91 and 93 have the higher percentage of this chain length thereby igniting at a lower but more predictable temperature and pressure range.Is this true or do I completely misunderstand???
 
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rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: premium gas

now I am confused.<br /> octane is simply a measure of the fuel to be consistently controled at a specific temp and burn rate. actually the higher the octane the slower the burn and in some motors high octane inhibits max horse power.
 
J

jimchere

Petty Officer 1st Class
Joined
Jun 30, 2003
Messages
321
Re: premium gas

Maybe outdated, but at when I worked at a gas station, the truck came by and filled all three underground tanks. I had a 15 gallon jug of "stuff" to add to the gas tanks...for mid-grade it was x-ounces, for premium xx-ounces. All there was to it. NO joke.
 
K

kenimpzoom

Rear Admiral
Joined
Jul 13, 2002
Messages
4,807
Re: premium gas

The number 87 is actually the R+M/2 method.<br /><br />Two ways to determine octane...<br /><br />One, via lab tests with high tech machines.<br /><br />The other, an actual one cylinder engine they run it in till it knocks.<br /><br />They average them together to get the number you see on the pump.<br /><br />Ken
 
B

beniam

Petty Officer 2nd Class
Joined
Feb 2, 2005
Messages
113
Re: premium gas

About octane ratings:<br /><br />Octane; A continuous chain Alkane (in English: a backbone of 8 carbons CCCCCCCC With all the outside free electron spots taken by a hydrogen, H)<br />Octane :CH3(CH2)6 CH3 . <br /> 8 carbons, 18 hydrogens<br /><br />Isooctane;also known as 2,2,4,trimethylpentane<br /><br />5 carbons in a row (pentane). CCCCC 3 methanes branching offsides ( methane CH3- one carbon, 3 hydrogens). 2,2,4 places of attachment of branch.<br /> 8 carbons, 18 hydrogens<br /><br />Heptane; 7 carbons,16 hydrogens, turns to vapor at lower temperature than Octane, also lower autoignition point. <br /> 7 carbons,16 hydrogens<br /><br />Autoignition; temperature at which fuel and air mixture self ignites (no spark required).<br /><br />Arbitrary standard (well we gotto use something, so octane rating seemed like a good idea at the time); ----Isooctane = 100 (minimal knock)<br /> ----heptane = 0 (bad knock )<br /><br />Autoignition temperature of isooctane =220 celcius, or 428 Farenheit.<br /> <br />As you compress a gas (mixture of air and fuel), it gets hotter. So at top dead center of piston stroke, want to be below autoignition temp.<br /><br />Soooo define octane 92; 92% isooctane,8% heptane.<br />Compare the mix you got with the 92 octane, and you got 92 octane equivalent.<br /><br />Actual content;variable mix, some parts of which are aromatics, and other C-H combos that burn fine, but you should not sniff too much off.<br /><br />Its a little more complex than all that, but is a start. Hope I did not confuse anybody. <br />And yes, I really dont have a life. My Ex periodically says so , so it must be true. Be happy, boat lots and spring is coming. Batavier
 
Kenneth Brown

Kenneth Brown

Captain
Joined
Feb 3, 2003
Messages
3,481
Re: premium gas

About octane ratings:<br /><br />Octane; A continuous chain Alkane (in English: a backbone of 8 carbons CCCCCCCC With all the outside free electron spots taken by a hydrogen, H)<br />Octane :CH3(CH2)6 CH3 . <br />8 carbons, 18 hydrogens<br /><br />Isooctane;also known as 2,2,4,trimethylpentane<br /><br />5 carbons in a row (pentane). CCCCC 3 methanes branching offsides ( methane CH3- one carbon, 3 hydrogens). 2,2,4 places of attachment of branch.<br />8 carbons, 18 hydrogens<br /><br />Heptane; 7 carbons,16 hydrogens, turns to vapor at lower temperature than Octane, also lower autoignition point. <br />7 carbons,16 hydrogens<br /><br />Autoignition; temperature at which fuel and air mixture self ignites (no spark required).<br /><br />Arbitrary standard (well we gotto use something, so octane rating seemed like a good idea at the time); ----Isooctane = 100 (minimal knock)<br />----heptane = 0 (bad knock )<br /><br />Autoignition temperature of isooctane =220 celcius, or 428 Farenheit.<br /><br />As you compress a gas (mixture of air and fuel), it gets hotter. So at top dead center of piston stroke, want to be below autoignition temp.<br /><br />Soooo define octane 92; 92% isooctane,8% heptane.<br />Compare the mix you got with the 92 octane, and you got 92 octane equivalent.<br /><br />Actual content;variable mix, some parts of which are aromatics, and other C-H combos that burn fine, but you should not sniff too much off.<br /><br />That pretty much sums it all up.<br /><br /><br />EDIT: I see as I was typing all of this Batavier already had it ready, or he can type faster than me. Ya right :)
 
LadyFish

LadyFish

Admiral
Joined
Mar 18, 2003
Messages
6,894
Re: premium gas

200503210625_mb_hlm1_i1_2_0
 
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DJ

Guest
Re: premium gas

For once-in seven years-AZ has the cheapest gas.<br /><br />$2.09-$2.11/gal-87 octane.<br /><br />I guess the "pipe"is fixed. :rolleyes:
 
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