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CA smog test: is high octane fuel really a good idea


barrys

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2010
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Ford
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[Note: discussion is based on my 1994 3.0 auto.]
I hope this doesn't sound like a moron question even though I am one when it comes to real tuning topics but...
I read all over and got advice from my mechanic to run high octane fuel for the smog test. The argument being that higher octane fuel has less impurities and therefore will burn cleaner. That made sense to me. I took this advice and got high numbers on repeated tests for hydrocarbons which I understand to mean "unburned fuel." What I'm curious about is what the engine design and computer tuning are expecting as far as fuel purity and how they compensate for the octane level in regular fuel which is what the truck is designed for and usually runs on.

So, trying to use proper terms here: If the truck is expecting a fuel mix based on the octane level in regular fuel, and we give it high octane, won't that be "perceived by the engine" as a rich mixture -- assuming the same amount of air is sent in -- which might make the combustion not burn all the fuel?

Just an interesting question. Perhaps a more interesting one is why not just change the catalytic converter which supposedly is designed for up to 80K miles and I ran mine for 130K. At that point, I passed on HC by only 3 ppm which barely passing.
 


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177CIOfPureLove

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Trust me, it works. Running a higher fuel grade in my experience ALWAYS lowers the ppm. I see what your saying, but it doesn't matter. I know it first hand and its on many other forums.
 


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