With my Chev 6.0 LS I find the oil will be dark brown on the dipstick by 5,000 miles, which means it’s black coming out into the pan. This happens to coincide with when I change it. The new oil always looks light brown the the dipstick, even if I leave the filter on for a 2nd go around. The oil in the filter is not enough to darken my new oil to any significant degree in my case. This engine has over 212,000 miles on it. YRMV.