I stay on top of the oil changes using Mobil 1 0W40. This engine has 253k miles on it averaging between 70 and 90 mph for most of that time. I've been changing oil at around 7500 mile interval.

rear lobe on #6, or last lobe on intake, bank 2.

This was only lobe like this. I wonder if a failing cam actuator could possibly have caused low oil flow to this lobe?

I meant to mention this is not that much of a job but there is a lot of stuff in the way that has to be removed to get to what you are working on.

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Jim