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Emissions test: regular, super or ethanol?

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Old Mar 15, 2007 | 09:17 PM
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Emissions test: regular, super or ethanol?

Gentlemen,

After just barely failing my emissions test last week, today I changed the oil & filter, new air filter, new spark plugs and a new oxygen sensor. Going back for the re-test on Saturday.

Will be making sure the engine is thoroughly warmed up - it'll go for a 15 minute highway drive and I'll probably leave it running while it waits.

Question: what gasoline produces the lowest emissions? Regular? Super? In my area there's also a gas station that sells regular with 10% (or maybe it's 5%) ethanol in it.

Thanks.
 
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Old Mar 15, 2007 | 09:24 PM
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I would use ethanol. If the Feds make it mandatory around urban areas to help clean the air, I would think it would do the same with your truck.
 
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Old Mar 15, 2007 | 09:37 PM
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Better drive for at least 30 minutes...
PCV valve?
 
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Old Mar 15, 2007 | 10:20 PM
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I'd go for the ethanol. Also some other things that might not hurt:

Plug wires
Chevron Techron fuel injector cleaner
Slightly heavier oil to prevent combustion chamber contamination
PCV valve (as mentioned)
 
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Old Mar 16, 2007 | 06:26 PM
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What part of the emission test did your truck fail? If the NOx is too high then ethanol may only exacerbate the problem.
 
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Old Mar 16, 2007 | 10:33 PM
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Use the regular(low octane) fuel. If you have a stock motor, running high octane will practically guarantee that you fail. High octane doesn't burn as quickly which will result in unburned gas coming out your tailpipe. I failed a smog test 4 times, changing timing and mixture while running high octane. I switched to low and passed with flying colors on the 5th test. IF you get the chance, grab a box of that "Guaranteed to Pass" stuff you see in parts stores and read the back. It will explain in better detail what I mean.
 
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Old Mar 19, 2007 | 08:14 AM
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Originally Posted by osbornk
I would use ethanol. If the Feds make it mandatory around urban areas to help clean the air, I would think it would do the same with your truck.
*If* the car is calibrated to run it. Otherwise, it might actually INCREASE emissions.

Ethanol requires a richer mixture and more timing to burn properly. Incomplete combustion and misfiring due to too lean of a mixture or insufficient ignition timing can lead to higher CO and HC emissions.
 
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Old Mar 19, 2007 | 11:04 AM
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Originally Posted by Bart99GT
*If* the car is calibrated to run it. Otherwise, it might actually INCREASE emissions.

Ethanol requires a richer mixture and more timing to burn properly. Incomplete combustion and misfiring due to too lean of a mixture or insufficient ignition timing can lead to higher CO and HC emissions.
If what you say is true, why does the government mandate that it be used in high pollution areas if most of the cars are not calibrated for it?
 
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Old Mar 19, 2007 | 11:51 AM
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Originally Posted by osbornk
If what you say is true, why does the government mandate that it be used in high pollution areas if most of the cars are not calibrated for it?
I think Bart was referring to E85 which is 85% ethanol. The ethanol content for regular gasoline is 10% at most.

Bart is correct about the "leaning out" effects of ethanol, which is why an engine that is making too much NOx is not going to be helped - and will probably be worse off - with E85 running through it. High NOx levels are caused by combustion chamber temperatures that are too high, and a leaner a/f mixture seems to be the last thing you would want.
 

Last edited by Rockledge; Mar 19, 2007 at 11:56 AM.
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Old Mar 20, 2007 | 09:34 AM
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Yes, I was referring to E85. As Rockledge stated, vehicles calibrated for regular gasoline can run up to 10% ethanol without any negative effect on emissions. Its somewhat up in the air if E10 causes a measurable decrease in fuel economy. Its hard to point the finger at E10 for small decreases per tank, when there are so many other variables that can cause a vehicle to lose 10-15 miles on a tank of gas.
 
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Old Mar 20, 2007 | 09:39 AM
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Originally Posted by Rockledge
I think Bart was referring to E85 which is 85% ethanol. The ethanol content for regular gasoline is 10% at most.
.
The poster specified 10% ethanol.
 
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