I have used Mobil 1 0w40 for the past 16,000 or so miles. I have changed oil and filter (Mann) every 4,000 to 4,500 miles. I have never had the oil stay amber colored for long. It seems to get dark quickly. For example, my current oil has only 2,500 miles and feels a bit gritty when run between my fingers. Car runs fine. Is anything-wrong going on here?

I may be just a bit paranoid. TIA