1slowCamaro

Which fuel is better for detonation resistance? Some say 93 because of the higher octane rating and some say 91 because its "clear gas" for off road use only. Both unleaded. Thanks!

justin

Mark C

God, I would hope its the oxygenated 93. I can't possibly see the argument otherwise. I mean, the octane number is nothing more than a rating of detonation resistance.

The only thing that you would have to watch out for is if you approach the limit of your 42's, or your fuel pump. Its because the methonal in the oxygenated gas has less power in a given volume, and you will use/need approximately 10% more fuel. If you are on the edge with the summer mix, this could put you over it.

Texas Terminator

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Mark C:
<strong> God, I would hope its the oxygenated 93. I can't possibly see the argument otherwise. I mean, the octane number is nothing more than a rating of detonation resistance.

The only thing that you would have to watch out for is if you approach the limit of your 42's, or your fuel pump. Its because the methonal in the oxygenated gas has less power in a given volume, and you will use/need approximately 10% more fuel. If you are on the edge with the summer mix, this could put you over it. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">hmmmm....not a chemist by any means, but, O2 is the much needed ingredient in combustion right? more air(O2) = leaner = detonation. would the non-oxygenated 91 not have more of a quenching effect without the added O2?

dug

iTrader: (10)

Looks like the 93 octane fuel would more resistant to detonation, where as the 91 would make more power.

1slowCamaro

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> hmmmm....not a chemist by any means, but, O2 is the much needed ingredient in combustion right? more air(O2) = leaner = detonation. would the non-oxygenated 91 not have more of a quenching effect without the added O2? </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">This is why I'm wondering which would be better. I'd say at least 95 percent of the gas stations up year run only oxygenated gas year round. The unoxygenated 91 octane is illegal for on road use. Its not like I care about that though. I usually run 100 octane unleaded and unoxygenated. But obviously I dont want to have my car tuned to 100 octane because what if I cant get it somewhere. That would be bad. So I need a secondary fuel and I cant decide which would be better.

In normal cars that require premium I'd say the 93 would be better because cars from the factory are plenty rich at WOT and could benefit from a little leaner mixture. However, the last thing FI guys need is a lean condition.

Mark C

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 1slowCamaro:
In normal cars that require premium I'd say the 93 would be better because cars from the factory are plenty rich at WOT and could benefit from a little leaner mixture. However, the last thing FI guys need is a lean condition. [/QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">He is not a chemist. This is got nothing to do with rich and lean. In the old days, you would have needed to change your jets to run this. Its why a car set up for alcohol needs twice as much fuel. But with computer engine management, 20% is no problem.

1slowCamaro

So what you're trying to say is that the computer will just add more fuel with the 93 than it would with the 91 in order to get the same A/F ratio?

By the way, the 93 octane is Holiday "Blue Planet" gas (AKA watered down). <img border="0" title="" alt="[Razz]" src="gr_images/icons/tongue.gif" />

If equal amounts of each fuel were added the 91 would resist detonation better right?

This sucks. Why dont they just offer regular (no poop added) 94 octane gas here like I've heard they do in other states. 20 cents more a gallon or whatever. It should still be an option. 100 octane unleaded is $3.00 per gallon here which I dont think is too bad.

Mark C

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 1slowCamaro:
<strong> So what you're trying to say is that the computer will just add more fuel with the 93 than it would with the 91 in order to get the same A/F ratio?

I believe this to be so. It has to be. How else can a car tell what kind of gas it has.


If equal amounts of each fuel were added the 91 would resist detonation better right?

I have no idea, but, equal amounts of fuel would never be added, unless you were running into some restriction.

This sucks. Why dont they just offer regular (no poop added) 94 octane gas here like I've heard they do in other states. 20 cents more a gallon or whatever. It should still be an option. 100 octane unleaded is $3.00 per gallon here which I dont think is too bad. </strong>

It was not until I logged onto these forums that I found out Sunoco 94 was not available everywhere. No idea why. But of course, right now its oxygenated.

</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

Mark C

Oxygenated fuel is simply 80% gasoline and 20% methonal. Its used in the Northern states to control air pollution in the winter.

Oh, and thats why he described it as "off-road".

<small>[ February 26, 2003, 12:58 PM: Message edited by: Mark C ]</small>