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Old Apr 25, 2020 | 09:14 AM
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Corey Allen
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Got an 03 6.8 with 234k. Miss at idle but other than that runs great. Noticed fuel mileage decrease but have replaced #10 COP plugs and new boots. Any suggestions would be appreciated. I do run sea foam and have replaced pcv valve and fuel filter within last 2 months. Air filter is new as well. No codes either.
 
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Old Apr 25, 2020 | 09:20 AM
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From: billings mt
never mind.
 
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Old Apr 25, 2020 | 10:03 AM
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No worries. Plugs and boots changed a week ago. COP # 10 changed a few months ago. I also have done the sea foam through the brake vacuum line as well and also every month or two run it in the fuel tank. Only run the 90+ octane premium as well.
 
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Old Apr 25, 2020 | 10:02 PM
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What kind of decrease are we talking about? 3 to 4 mpgs from one tank to the next is pretty normal depending on the way you were driving. Are you calculating it by hand?
 
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Old Apr 26, 2020 | 11:48 AM
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Yes

Originally Posted by phillips91
What kind of decrease are we talking about? 3 to 4 mpgs from one tank to the next is pretty normal depending on the way you were driving. Are you calculating it by hand?
I always calculate by hand. And yeah around 3-4 mpg. I drive easy don't really tow anything or have a lead foot.
 
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