4.7 HO - Use hi-octane?
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Joined: May 2010
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From: Wesley Chapel, FL
Here is what it says from my 2005 manual
The 4.7 HO engine is designed to meet all emissions regulations and provide satifactory fuel economy and performance when using high quality unleaded gasoline having an octane range of 87-91. The manufacturer recommends the use of 91 octane for optimum performance.
Like I told you in your other thread traka. You can use 87 octane (regular) no problem, which is what i use, but if you want the optimum performance use 91.
The 4.7 HO engine is designed to meet all emissions regulations and provide satifactory fuel economy and performance when using high quality unleaded gasoline having an octane range of 87-91. The manufacturer recommends the use of 91 octane for optimum performance.
Like I told you in your other thread traka. You can use 87 octane (regular) no problem, which is what i use, but if you want the optimum performance use 91.
Last edited by Brian9; Jul 31, 2010 at 06:22 PM.
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From: Louisiana
The PCM is set up with a high octane and a low octane timing table. It will use the high octane table until it sense knock and then drop to the low octane timing table. So you can run 87 if you want, just won't get the maximum performance.
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From: South Georgia/East Florida
The 4.7 HO (at least the model in my Grand Cherokee) has dual knock sensors and will adjust to 87 octane fuel. So according to manufacturers specs, using that grade of gas is fine, just with degraded performance.
That said, just like with the Hemi (which recommends 89, but says in the manual you can use 87), whenever I hear about a 4.7 HOs having a major cylinder failure, it seems that the owner admits to using 87 octane fuel on a regular basis.
I've never run anything lower than 91 octane in my GC. But I have done testing on my Hemi (pre-Superchips) and found that the increased fuel economy running 93 octane more than made up for the difference in cost between 89 and 93 octane fuel, so I don't even mess with ANYTHING under 93 in either of my vehicles, unless I'm on vacation in areas that have 91 or 92 octane as opposed to 93...
That said, just like with the Hemi (which recommends 89, but says in the manual you can use 87), whenever I hear about a 4.7 HOs having a major cylinder failure, it seems that the owner admits to using 87 octane fuel on a regular basis.
I've never run anything lower than 91 octane in my GC. But I have done testing on my Hemi (pre-Superchips) and found that the increased fuel economy running 93 octane more than made up for the difference in cost between 89 and 93 octane fuel, so I don't even mess with ANYTHING under 93 in either of my vehicles, unless I'm on vacation in areas that have 91 or 92 octane as opposed to 93...
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Higher octane is used to reduce knock, and the HO loves to knock with regular gas during "spirited" driving. If you drive hard, Use a higher octane, if not, then I would guess that a lower octane would be fine.
Are there any mods done to this truck? like an exhaust/intake? Anything that increases airflow has the potential to increase knock counts also... just tossing that out there.
Are there any mods done to this truck? like an exhaust/intake? Anything that increases airflow has the potential to increase knock counts also... just tossing that out there.