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Old 10-23-2009, 07:45 PM
Dodge Ram Forum Senior Member
Join Date: Sep 2009
Location: Virginia Beach, VA
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Vehicle: 2008 Dodge Ram 5.7L HEMI
Trim Level: Big Horn, Quad Cab
Color: Black
Engine: 2003-2008 345ci (5.7L) Hemi V8 345hp 375lb/ft
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Ok, you are right in saying that 91 octane burns slower, but it burns slower for high compression ratio vehicles, thats its purpose...High octane in a low compression ratio vehicle does in fact burn slow too, but decreases the engine performance and increases the work load of the engine...In case you do not know, the octane reading for fuel, ie 87,89,91,93, is a misconception to most people...By that i mean, most people believe, "im gonna put premium in my car cuz it has higher octane which will give me better mpg, and more hp", when in fact they are wrong...The numbers do not mean that the 91 fuel or 93 fuel is better to run than 87 for gains in mpg and hp...the numbers represent the resistance of fuel to knocking and pinging in any engine, which is where the fuel is not able to be burned off as normal, which can obviously damage your engine...So what happens when you raise the compression ratio on an engine??? Well, you in fact raise the chances to create knocking and pinging, which is why they have premium fuel with higher octane, which burns slower to ensure a smooth running engine...
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