My brother got a 2007 RAM 1500 4.7L with 96000 miles on it. He drove 6k miles on it over the past 6 months, without changing oil. Oil was level when he got it. Obviously, it was not smart of him to not replace the oil immediately and not check it more frequently.
6k miles later and 6 months later we checked the oil and it was well below level and very black. We drained only 3 quarts. This engine takes 6 quarts. Replaced filter and filled with full synthetic.
There is an oil pressure gauge, which is operational and never went to zero while he was driving. Which makes me believe 3 quarts was enough to cover the oil pump intake pipe.
The new full synthetic we put in looks dark on the dipstick immediately after replacement. Which makes me suspect the presence of at least some sludge which formed when driving on old hot decomposing oil. We plan to replace oil and filter again in ~500 miles.
What else should we look for to understand the extent of the damage? Measures to take to mitigate?