The darker color of the oil indicates that its detergent is doing its job and it is not an indication of its effectiveness.
There are quite a few performance cars use M-1 full sync as factory fill and the oci is more than 10k miles.
However, it doesn't hurt anything if change at 5k miles.
Quote:
Originally Posted by ssmoked
I run full synthetic Mobil 1 and after 5000 miles the color is pretty dark brown. To play it safe, I would change every 5k if I were you
I do drive hard daily though
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