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Discussion Starter · #21 · (Edited)
Now you've gone and ruined all my fun...of which I had clearly implied I was having. :)

There are a lot of variables that the manual cannot predict including altitude, humidity, ambient temperature, engine temperature, all of which can significantly encourage detonation....

That is true
However, I'm sure chrysler engineers have taken all of that into consideration when manufacturing the 5.7.
Otherwise the manual would have stated: USE A GASOLINE WITH AN OCTANE RATING OF 89

instead of stating 87-89
 

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That is true
However, I'm sure chrysler engineers have taken all of that into consideration when manufacturing the 5.7.
Otherwise the manual would have stated: USE A GASOLINE WITH AN OCTANE RATING OF 89

instead of stating 87-89
Well I'll be? There may still be fun to be had...:)

So are you sure that the Chrysler engineers took all this into account the same way the Ford Pinto engineers took the placement of the gas tank into account? Or are you sure the same as the Toyota engineers were sure about their gas pedal/floor mat? And what makes you think that it was the engineers that had the final say? Do you think marketing and legal had a hand in it? Which manual are you referring to, the users manual or the service manual. My service manual, Section 2-4 says only 89 octane period.

It also may interest you to know that each of our 50 states can set gasoline standards. It may also interest you to know that state laws are written by state legislators that just happen to be lobbied by the refiners, distributors, and suppliers. My state doesn't even require anything over 90 octane. So guess what, we have premium 90 octane gasoline!

The 5.7L is sold around the world including northern Canada and Alaska as well as on the other extreme Saudi Arabia. The engine may be used 15 minutes at a time as a grocery getter or used to haul a trailer back and forth between Denver and Grand Junction. Do you really think the Chrysler engineers would recommend the same octane gas for all? And even if they would, would you want to use the same octane gas? Part of the challenge these days is that the internet connects us all instantaneously around the world and our customs and habits just haven't caught up yet. Your particular geography, gasoline quality, driving habits, performance expectations, and risk aversion all play into what octane gas you should choose. To pick one number out of one book and say it will work for everybody around the world may be a little naive.
 

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Discussion Starter · #23 · (Edited)
Well I'll be? There may still be fun to be had...:)

So are you sure that the Chrysler engineers took all this into account the same way the Ford Pinto engineers took the placement of the gas tank into account? Or are you sure the same as the Toyota engineers were sure about their gas pedal/floor mat? And what makes you think that it was the engineers that had the final say? Do you think marketing and legal had a hand in it? Which manual are you referring to, the users manual or the service manual. My service manual, Section 2-4 says only 89 octane period..

Manufactures defect.
Thus, the manufacture is liable


Well I'll be? There may still be fun to be had...:)

So are you sure that the Chrysler engineers took all this into account the same way the Ford Pinto engineers took the placement of the gas tank into account? Or are you sure the same as the Toyota engineers were sure about their gas pedal/floor mat? And what makes you think that it was the engineers that had the final say? Do you think marketing and legal had a hand in it? Which manual are you referring to, the users manual or the service manual. My service manual, Section 2-4 says only 89 octane period.

It also may interest you to know that each of our 50 states can set gasoline standards. It may also interest you to know that state laws are written by state legislators that just happen to be lobbied by the refiners, distributors, and suppliers. My state doesn't even require anything over 90 octane. So guess what, we have premium 90 octane gasoline!

The 5.7L is sold around the world including northern Canada and Alaska as well as on the other extreme Saudi Arabia. The engine may be used 15 minutes at a time as a grocery getter or used to haul a trailer back and forth between Denver and Grand Junction. Do you really think the Chrysler engineers would recommend the same octane gas for all? And even if they would, would you want to use the same octane gas? Part of the challenge these days is that the internet connects us all instantaneously around the world and our customs and habits just haven't caught up yet. Your particular geography, gasoline quality, driving habits, performance expectations, and risk aversion all play into what octane gas you should choose. To pick one number out of one book and say it will work for everybody around the world may be a little naive.
Dude, my head hurts now from all this serious thinking
LMAO

I'm going to use the gas that I can afford at the time I'm getting gas.....LOL

Years ago, wasn't there a grade of gasoline that was lower than 87
 

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Yeah... and there still is... During our recent trip out west... in the mid-west where E85 is available, the Shell stations have "Regular" as 85 octane, "Intermediate" at 87 octane and cheaper because of, like, 15% ethanol, and then 89 as the "Premium" grade. I thought this was completely ridiculous.

Here in WV, everything is 10% ethanol because of our regions seasona and/or pollution score (or something like that) and Shell's grades are 87, 89 and 92 octane.
 

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Manufactures defect.
Thus, the manufacture is liable

Dude, my head hurts now from all this serious thinking
LMAO

I'm going to use the gas that I can afford at the time I'm getting gas.....LOL

Years ago, wasn't there a grade of gasoline that was lower than 87
I hear ya! My office is located just across the street from a Shell station and they have been upping the price every day for the last month. It is now $4.30 a gallon for 90 octane! If you've got a programmer like the Predator just monitor your knock and if it doesn't pull more than 5 degrees of timing your probably going to have a hard time telling the difference. Another tact could be installing a water injection kit to come on at peak torque. At near 30 cents a gallon difference it wouldn't take long to pay for the kit and you would still be completely safe with no performance dip.
 

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also higher octane burns hotter so if you can use 93 or 91 and get the same results then use the lower octane. but this practice is only advised if you really know what yr motor is doing. that means lots of data logging or lots of dedicated dyno time. Also the higher elevation you go less octane will yield the same result as a higher octane in Texas.
 

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also higher octane burns hotter so if you can use 93 or 91 and get the same results then use the lower octane. but this practice is only advised if you really know what yr motor is doing. that means lots of data logging or lots of dedicated dyno time. Also the higher elevation you go less octane will yield the same result as a higher octane in Texas.
A couple questions for you...
In what way does higher octane burn hotter?
How are you rationalizing that higher elevations need less octane? Are you considering the adaptive qualities of our PCM?
I can guess as to what you mean but I would appreciate you explaining it in more detail so I won't misinterpret what you are getting at.
 

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Higher octane does not burn hotter, it is merely more resistant to pre-ignition, which is what high performance engines require.
As elevation increases, the need for octane decreases, as the air thins out around you. You'll note that places with high elevations have lower octane fuel available at their fill stations.
 

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Higher octane does not burn hotter, it is merely more resistant to pre-ignition, which is what high performance engines require.
As elevation increases, the need for octane decreases, as the air thins out around you. You'll note that places with high elevations have lower octane fuel available at their fill stations.
A substitute answerer will do...:) Check on number one, but with number two maybe not so much. Higher elevations have less air density but the same ratio of nitrogen and oxygen. Your MAP will be less so adaptives will adjust fuel. Net result is that it won't matter so long as the MAP is right. Now with a carbureted engine it would be different and the car tuned at sea level would run richer and presumably safer at altitude, but that is kind of a long shot as most carbureted cars driven at altitude would presumable be tuned at altitude. Maybe the fact that it is colder on average at altitude the gas can be justifiably have a lower octane?
 
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