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Old 01-03-2022, 08:37 PM   #1
Nickelcharlie
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Join Date: Sep 2016
Location: Cleburne, Texas
Posts: 83
What oil are you using in an older flat tappet motor?

I have an 86 GMC with the original flat tappet motor. Should I be using an oil such as Rotella made for diesel motors or can I use a synthetic oil? I have also read once a flat tappet motor has been broken in correctly a synthetic oil can be used! So I would like to hear what you have been using successfully in your older motor for a long period of time?
My owners manual lists multi grade oils so I am thinking it is alright to be using any brand quality oil. Thanks for your input in advance!
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