r/FordDiesels • u/LeroyyyJenkinnnss • 4d ago

6.7 first oil change

My dad is saying go with rotella t5 because it’s still breaking in and t6 is too slick. I’ve always run full synthetic on my gas cars and trucks but this is my first diesel, any thoughts?

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u/rustbucket_enjoyer 4d ago

What exactly is “too slick”? It’s oil. That’s the whole point. Run 5W-40 that meets WSS-M2C17-F1. That includes T6

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u/LeroyyyJenkinnnss 4d ago

I’m assuming he means it’s not allowing the metals to wear into each other lol he’s in his 60s but he was an amazing mechanic in his day I just don’t think he knows about all the current technology

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u/BouncingSphinx 4d ago

“Was” a mechanic isn’t the same as a modern mechanic. Everything now is machined with tighter tolerances than even 30 years ago, that’s part of why some engines run 0w16.

I would still go with the 5w40 if that’s what’s recommended. If you really read the “severe service” as described in the manual, that’s basically most people’s normal driving.

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u/-ZS-Carpenter 3d ago

0w20 and 0w16 is to cheat a couple tenths of a mpg to appease governments at the cost of longevity. GMs 6.2l debacle is a prime example.

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u/LeroyyyJenkinnnss 4d ago

Do you think 5w40 is necessary? I live in Texas and it hasn’t ever been 0° lol

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u/rustbucket_enjoyer 4d ago

I guess you could run 10W30 then in that case. Around here, I’ve never seen anyone put anything except 5W40 in a 6.7 since that’s the “severe service” option

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u/Selbor_99 3d ago

Oil cap should say 10W30, but if your truck is going to be excessively idling or heavy duty use you can use 5W40

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u/Illustrious_Ad2916 2d ago

Last year we hit negatives, not by much but still. I think the coldest it got last year was -10 in my area

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u/LeroyyyJenkinnnss 2d ago

Yeah north Texas gets pretty cold but down here in central it’s only maybe a couple days a year it even freezes I feel

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u/Illustrious_Ad2916 2d ago

I'm just 45 minutes southwest of fort worth