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6.6 Fuel Requirements

JimBuck

By JimBuck
in 6.6L Gas V8 (L8T)

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TrailBoss1 Enthusiast

TrailBoss1

Posted
Posted

The 6.6 runs a fairly high compression ratio. Although it doesn’t require premium, and I believe the horsepower and torque ratings assume regular fuel, do you feel you get a benefit from the higher octane? Have you compared fuel mileage, throttle response, etc.? 

ShotgunZ71 Senior Enthusiast

ShotgunZ71

Posted
Posted

I've run 87 since new, towing or otherwise. Running a higher octane may help when towing, but I can't say for sure. 

redwngr Senior Enthusiast

redwngr

Posted
Posted (edited)

OM says 87 for all gasoline engines except the 6.2 which it recommends 93.

Edited by redwngr
Colossus Senior Enthusiast

Colossus

Posted
Posted

You can try running premium a few tanks and see how she responds.  if you notice a good difference, feel free to stick with it, otherwise if it does just fine off of 87/89 go for it. 

Stand By Enthusiast

Stand By

Posted
Posted

These are variable timing aren't they? The computer sets the timing and torque to your needs. I've run 87 for over 5000 miles without a hiccup. Including some heavier towing in hot weather. Dealer gave me the truck with a full tank and never advised to do anything special with it.

Ray Pickle Enthusiast

Ray Pickle

Posted
Posted

87 is what it is tuned to run on. I doubt computer will have parameters for higher octane in stock configuration. So far no aftermarket tuning options to take advantage of octane increase.

Colossus Senior Enthusiast

Colossus

Posted
Posted

The computer will adjust the timing somewhat depending on what you are running.  You might find better MPG and performance running on premium, or you might find it runs best on 89 or 87.  Try them a few times and decide for yourself. 

  • 4 weeks later...
Dunn Senior Enthusiast

Dunn

Posted
Posted (edited)
On 9/30/2020 at 3:21 PM, redwngr said:

OM says 87 for all gasoline engines except the 6.2 which it recommends 93.

thats what i read as well.......i ran 91 a few times couldnt tell a difference

Edited by Dunn
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  • 1 year later...
webperson04 New Member

webperson04

Posted
Posted

I ran 87 for first 2000 miles and noticed 6-9 mpg towing and 10-14 mpg not towing. I switched to 91 octane premium and noticed significantly improved fuel economy (8-12 towing and 12-18mpg not towing. At a conservative 25% improvement, I'd say premium is worth it. 

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