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Old 12-05-2011, 08:53 AM   #27
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Join Date: Jul 2011
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Location: Victoria B.C., Canada
What I Drive: 2008 MazdaSpeed 3

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Originally Posted by BowerR64 View Post
Its true in a way, stock the car is "tuned" to run that gas. I believe they retard the timming to allow the cheap fuel to run ok in it.

You start to tweak it with a tune and you bump the timming way up and then the cheap gas starts to cause knock and then the car backs off the timming like in the pictures i posted.

When you get a tune it says premium fuel only and this is why because there IS a difference. It burns better, cleaner or something and im sold on the better gas now.

Why does the cheap fuel cause knock and what is it they put in it that does it? i dont know but i like my car so im not going to put junk in it if there is better stuff right next to it.

A few weeks ago i went to a cheap mom and pop gas station and i filled up with their premium because i was about out and knew i couldnt make it to my regular station. I swear i thought something was wrong with my car. It lost some of its zip i wasnt sure what was wrong it didnt run rough or anything it just didnt have the same zip it did.

After that tank was done i filled up with my normal 92 premium from the BP near the airport i usualy go to and i instantly felt the difference.

If i ever get in a pinch again with fuel im using just what i need to get back to the regular station and thats it.

Their premium must be low grade or something it just wasnt right.

I even had Tom tell me once after i posted a datalog and he asked me what fuel i was using because it was junk and it wasnt the same stuff i posted in an earlier log he adjust the tune to. This was early before i found a good fuel my car was happy with. The junk fuel was from quick trip at that time.
The graph you posted is pretty useless. Its just to cluttered and you really can pull any information our of it, the scaling is all wrong. When posting data logs its usually best just to post up a spread sheet. Its a lot clean.
2008 Victory Red MazdaSpeed 3 - Not stock and self tuned.
2012 Sterling Gray Focus Ti - K&N.
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